US foreign policy is entering an era of change - the most significant one since the days of Harry Truman’s administration. The cause of such changes lies in the discrepancy between the US foreign policy consensus reached back then and forged in the 1990s and the current (and, most likely, future) global trends.
The presidential race in the United States has entered its final stage. It's time to pause and take stock. First of all, the current campaign has revealed deep fissures not only between Democrats and Republicans, as has been the case in all recent elections since 1996 (Bill Clinton vs. Bob Dole) and especially in 2000 (George Bush vs. Al Gore) and 2008 (Barack Obama vs. John McCain), but also between the entire US foreign policy elite and society. The nature and depth of the divide is reminiscent of the isolationists and internationalists during the times of Woodrow Wilson and Franklin Roosevelt, and shows the limits of foreign policy consensus in the United States. This consensus first emerged in the 1940s when Harry Truman was president. It grew stronger after Washington declared victory in the Cold War and started actively working to shape the world in the mould of its ideas and values, which seemed universal back then.
This consensus, shared by Democratic liberal internationalists and Republican neoconservatives alike, is based on four pillars: 1) a commitment to "global leadership," 2) a commitment to strengthening and broadening the "liberal international order", 3) recognition of the inextricable link between the influence, safety and prosperity of the United States, on the one hand, and its leadership of the "liberal international order," on the other hand, 4) a commitment to spreading democracy. In turn, this implies the preservation and even the expansion of the US global presence and greater intervention to resolve the most important international and even domestic issues and crises.
The problem, however, is that the implementation of this consensus was based on several axioms about the world and the place of the United States in it, and faith in these axioms buoyed public support over the course of 70 years. According to these axioms, the world develops linearly and, in general, in a way that redounds to the benefit of the United States and its ideology (the "end of history" concept); the American ideology is universal; the world needs and welcomes American leadership; globalization is good for America and, by participating in it, countries and regions reduce the likelihood of conflicts and begin to play by the rules established by the United States; the spread of democracy and the market economy automatically expands peace, security and prosperity; and the belief that Americans, like the Western population in general, will be better off tomorrow than yesterday. The current US foreign policy consensus received a vast infusion of legitimacy at the end of the Cold War, which seemed at the time to confirm many of these assumptions.
Today, it is becoming increasingly clear that these axioms were illusory. Moreover, unlike the elite, which continues to believe in them and is desperately trying to prove their relevance, the US population is experiencing this the hard way. Fifteen to 20 years after the greatest triumph of the West and the United States, the world ceased to move in a direction that is good for them. It turned out that globalization has a "dark side" (global financial and economic crises, the general vulnerability of all to all and transnational security threats) and, in general, is working for non-Western countries much better than for the West. Against this backdrop, an unusually tough statement by President Obama that the United States, not China, will write the international trade rules in the 21st century, and Donald Trump's promises to bring industrial production back to the United States are symptoms of one and the same disease. Globalization as is no longer suits the United States. It is decimating the middle class, reducing living standards and comes as a blow to the progressive ideology of the United States as the realization sinks in that today's children may be worse off than their parents.
The same applies to security. The end of the Cold War failed to bring about Kant's "perpetual peace." On the contrary, the world is becoming increasingly torn by conflicts, less governable and more hostile toward the United States and the West in general. Transnational threats are growing in the wake of the renewed rivalry between great powers, and the United States, as the self-styled leader, is absolutely powerless to do anything about it. Washington's attempts to intervene and play the role of a "global policeman" usually make things worse. Just look at Iraq, Afghanistan, Libya, the Greater Middle East, and Ukraine.
The same goes for migration, which has become a major challenge to social development and identity, both in the United States and Western Europe. American society was not ready to cope with the ceaseless influx of Latin American immigrants. The melting pot, which worked so well for European Americans, did not simply falter, but actually collapsed. The white population, which will likely become a minority by mid-century, has found itself under siege. Therefore, the growing terrorist threat from Islamic radicals has predictably prompted an even greater surge of intolerance.
Simply put, faced with the uncontrollable forces of globalization and a less hospitable world, American society - or, at least, a significant portion of it – has started opposing the foreign policy consensus advanced by the political elite for several decades now. Society demands the familiar and friendly "yesterday" and instinctively seeks to fence itself off from an increasingly hostile world, both nearby Mexico and overseas Europe, the Middle East and so on. Donald Trump is on the front line of this protest. He is popular precisely because his populist statements resonate with the public mood and the general rejection of the previous foreign policy consensus (and the elite behind it).
Importantly, all the Republican candidates and almost all Democratic ones (with one exception), who represented the traditional political elite and the traditional foreign policy consensus during these elections, failed miserably. On the contrary, the critics of the system, such as populist Donald Trump, socialist Bernie Sanders and Tea Party leader Ted Cruz, became the stars of the campaign. Against this backdrop, Hillary Clinton is a kind of "last of the Mohicans." She is the only representative of the establishment and the guarantor of the status quo, who has made it to the finals.
As a result of the chasm between the traditional elite and an angry electorate, presidential candidates, for the first time since the first half of the 20th century, are running campaigns based not merely on differences of opinion but on fundamentally different foreign policy paradigms.
The foreign policy views of the Democratic nominee were shaped in the 1990s and represent a concentrated form of the traditional American foreign policy consensus. She is a proponent of US global leadership and the US-led "liberal international order," and a true candidate of the American elite, who were disappointed in George W. Bush and Obama, considering the policy of the former excessively rigid and lopsided, and the policy of the latter too soft and accommodating. No wonder the majority of foreign policy elites began to coalesce around her during the initial stage of the election campaign. First, there were the Democrats who believed that President Obama does not do enough to advance US global leadership and does too little to promote American interests and even less to promote American values. Later, when it became clear that the Republican candidate Trump was winning, neoconservatives scrambled to throw their support behind her.
Indeed, in terms of her foreign policy outlook, Clinton is a cross between Barack Obama and George. W. Bush. Like Obama, she believes that the United States should promote the "liberal international order" and believes that the global standing of the United States is inextricably linked to the existence of this order and US leadership of it. But like Bush, she believes that the United States should not think twice about using military force, even in violation of international law, to defend this order, as well as US values and interests. Her rhetoric during the current campaign, and the statements by her closest allies, her track record as Secretary of State, as well as her previous foreign policy positions suggest that Clinton is a "hawk" and a "liberal interventionist." If elected president, she will conduct a more ideology-driven and tougher policy than the Obama administration. The foreign policy portion of the election platform adopted at the Democratic Party's convention in Philadelphia clearly shows this. It's filled with rhetoric about leadership and the "liberal order," promoting democracy, and deterring "Russian aggression."
Clinton is not devoid of pragmatism. Her entire political career, and particularly her current campaign, proves that she doesn't think twice before acting unscrupulously and, for the sake of political expediency, she does things that are at odds with the generally accepted American values and norms that she herself upholds. However, this is what Hillary Clinton normally does on domestic policy. When it comes to foreign policy, she has strong ideas about what's right and what's wrong, which direction the world should go in and what role the United States should play in it. Given the almost unanimous support of her approach to foreign policy by the foreign policy establishment in both parties, there is no reason to believe that, if elected president, she will suddenly abandon or significantly adjust them. In this context, her tendency to ignore norms and principles when it is politically expedient may result in not only foreign policy pragmatism, but also in a willingness to break international law if it is in the tactical interests of the United States. It's no accident that Secretary of State Hillary Clinton tried to persuade Barack Obama to use military force in Syria, and to thereby commit an act of aggression.
Even though Trump does not have detailed foreign policy views and is guided mostly by his business instincts and pure pragmatism, he demonstrates a fundamental departure from the established US foreign policy paradigm. He understands the disaffected voters who, on the one hand, would like to fence themselves off from a hostile world and concentrate resources on domestic issues and, to be frank, to put an end to globalization, but, on the other hand, are not satisfied with the Obama administration's "weak" policies. Judging by his remarks and the comments of his advisers, Trump intuitively leans toward a combination of classical political realism with a focus on national interests and little interest in values and the international order (as a set of rules and norms of behavior), and neo-realism with its strict approach to global alignment of forces.
Denying the link between US greatness, on the one hand, and its leading role in the liberal international order (the American system of alliances, trade and economic blocks and international economic institutions) and the desire to transform the international system in accordance with the US interests and values, on the other hand, is one of the key premises underlying Trump’s foreign policy outlook. It is no coincidence that one of the most respected American diplomats, former ambassador to the UN, Iraq and Afghanistan, Zalmay Khalilzad, described Trump’s foreign policy platform as a kind of throwback to the days of Franklin Delano Roosevelt. 
If you remove the fluff of outrageous and controversial remarks from what Trump is saying, one can see that his agenda is largely in line with the concept of offshore balancing, which has for several years now been promoted by leading American realists. 
In accordance with this view, the United States should reduce its direct presence in different regions of the world (except where it is needed to protect vital interests) and shift a greater burden of responsibility for security in respective regions to its allies, take a very selective approach to direct involvement in crises, refrain from using military force as a primary foreign policy tool, especially from occupation and nation-building missions, and reduce its democracy promotion activities.
This concept (and the school of realism in general) also recommends that the United States focus on relations with other great powers and develop policies toward them that will allow them to retain their superiority as long as possible.
Even with regard to specific foreign policy issues, Trump’s controversial remarks, if, again, you separate them from the populist wrapper, are completely consistent with the leading American realists’ recommendations. Thus, his remarks to the effect that European countries should protect themselves, and NATO has run its course are, in fact, no different from John Mearsheimer and Stephen Walt calling for complete withdrawal of US troops from Europe (even now, despite the Ukraine crisis and the worsening standoff with Moscow) 
, and especially from the statements by former US Defense Secretary Robert Gates who said that Washington might reconsider its approach to the alliance and its usefulness for America, which he made back in 2011. 
Trump's remarks about Russia and China and the role that he assigns to relations with other great powers in his foreign policy agenda (if it can be referred to as such), are also broadly in line with the realistic paradigm. With regard to China as a major economic and political rival, the United States formulated a strict policy of containment. Trump has already made it clear that he will not try to build partnerships with Beijing, and not only because of the job drain to China. A more constructive foreign policy has been proposed with regard to Russia, which is, of course, perceived as a great power, but not one that can pose a major challenge to the United States or call into question its global superiority. Apparently, realist-minded advisers to the Republican nominee hope to use the proposed partnership with Russia in order to more effectively contain China. If this is the case, this factor may become one of the major irritants in relations between the two countries should Trump be elected president.
This does not mean, though, that if elected Trump will really embark on a foreign policy course similar to Henry Kissinger or George H.W. Bush. Since Congress, the elite, the government bureaucracy and the media are against it, it is simply impossible. To a larger number of employees of the State Department and the Pentagon, even the current US foreign policy seems to be not tough enough and occasionally defeatist (remember the letter written by 50 employees of the State Department that called on Barack Obama to start bombing Syria like they did in Yugoslavia). With regard to Trump, there may be instances of sabotage or mass layoffs. Clearly, if he is elected president, his actual policies will be significantly different from his current statements. Already the choice of Mike Pence - a representative of the traditional Republican establishment with orthodox foreign policy views, including in relation to Russia - as a running mate demonstrates the inevitability of a major correction.
Yet, major changes to US foreign policy will take place no matter what. It is hard to tell exactly how, but Trump, if elected, will make a major move away from the dominant foreign policy paradigm in the United States over the past 70 years. US would be more hostile toward China, tougher and more pragmatic toward Europe, more pragmatic and neutral toward Russia, and more indifferent toward the Middle East. Most likely, there will be an attempt to once again reset US-Russia relations, this time on a new realistic basis of an informal "exchange of interests." US foreign policy will become even more one-sided, and the traditional bilateral US-Russian nuclear arms control inherited form the Cold War will eventually become a thing of the past. This is not good or bad. From the point of view of Russia's interests, there are both positive and negative aspects. In any case, it will not be the traditional policy of maintaining US "global leadership" or strengthening the US-led "liberal international order."
If Clinton wins, she will enjoy the support of the elite and the establishment of both parties on foreign policy issues for some time. The new administration will build on this to do what the Obama administration has not done or done poorly.
However, this period will not last long. The deep schism between the elite and society and the rejection of the traditional foreign policy consensus by a large portion of the electorate will only grow deeper. Therefore, Hillary Clinton's foreign policy will be criticized by society in the form of new populist leaders, and already in the 2020 elections she will be faced with new "trumps." Popular protest against the status quo will make itself felt with a vengeance. In 2024, the candidate of the "anti-elite" may well win.
Thus, US foreign policy is entering an era of change - the most significant one since the days of Harry Truman's administration. The cause of such changes lies in the discrepancy between the US foreign policy consensus reached back then and forged in the 1990s and the current (and, most likely, future) global trends. Maintaining "global leadership" in a multipolar world is impossible, and the "US-led liberal international order" in the traditional American understanding has not taken root.
It is just a matter of time. If Trump wins, the departure from the current consensus will begin in 2017. If Clinton wins, it will begin a little later. But it is inevitable.
 Zalmay Khalilzad. The Emerging Trump Doctrine? // The National Interest. July 29, 2016. http://nationalinterest.org/feature/the-emerging-trump-doctrine-17176
 John J. Mearsheimer and Stephen M. Walt. The Case for Offshore Balancing // Foreign Affairs, July/August 2016.
 Gates rebukes European allies in farewell speech // The Washington Post. June 10, 2011. https://www.washingtonpost.com/world/gates-rebukes-european-allies-in-farewell-speech/2011/06/10/AG9...