What kind of president do we need to face arguably the most dangerous set of international crises since World War II? After watching a marathon of raucous debates, town halls and interviews, a reasonable observer might conclude that just a very few of the remaining Republican and Democratic candidates have the depth of international experience, maturity and judgment to handle the most difficult job in the world.

And if a candidate with little understanding of global politics and national security actually wins in November, what are the real world consequences for the U.S. and our many allies who depend on a competent American leader in the Oval Office?

These are not idle questions when the two victors in the New Hampshire primary, Bernie Sanders and Donald Trump, lack both professional experience and a strong grasp of global issues. They would likely have a difficult time with the crises in the news just this week — North Korea’s nuclear threat, the Middle East wars and the Zika pandemic — much less the many more like them in President Obama’s foreign policy inbox.

A Trump victory would be disastrous for America’s reputation and leadership of the international order. His gross bigotry toward Mexico and the Muslim world, and open admiration for Russian President Vladimir Putin, have made him a scandalous figure internationally. At the Munich Security Conference last weekend, I was struck by the number of Europeans who, without exception, told me a Trump victory would be detrimental to American credibility. Trump is brutish and a bully who is loose with facts and short on discipline. He lacks the dignity, decorum and maturity that we should want our presidents to have on the international stage.

Sanders, in many ways, is everything Trump is not — a man of decency, intelligence and purpose. In his long career in public service in Vermont and the Congress, however, he has demonstrated little interest in global politics, and it shows in the debates. His foreign-policy focus seems cast backwards almost exclusively on the Iraq War. But he has not developed a coherent strategy for what we should do about Iraq in 2016. When he has made specific policy suggestions, they tend to betray a lack of sophisticated insight about the countries and leaders the president has to deal with.

Sanders’ most serious deficiency, however, could be in his capacity to lead as commander in chief in a dangerous 21st century world. It is difficult to imagine he’d have the confidence of our military, or understand how to use America’s Foreign Service effectively during a crisis.

Having served in the White House in the George H.W. Bush and Bill Clinton administrations and overseas as a U.S. diplomat, I don’t need convincing that the American presidency is the toughest job in the world. In fact, there is nothing close to it in sheer degree of difficulty.

Think of the job description. The president is CEO of the largest, most complicated institution in our country — the federal government. With a multitrillion dollar budget and millions of employees to manage, he or she must also pursue peaceful relations with 194 other nation states, form posses to corral troublemakers such as Iran and Syria, keep the Russians and Chinese in check, and lead the world on issues as diverse as climate change, cyber threats, and crime and drug cartels. The president is also the only person in our society entrusted with authority over our nuclear weapons to defend the country.

Of the remaining candidates, Republicans Jeb Bush and John Kasich have both run large state governments, have been active in national politics and have, by experience and interest, a good grasp of America’s place in the world.

But neither has the specific and deeply rooted experience Clinton earned as secretary of State, senator from New York and first lady in her extraordinary, indeed unique, service to our country. That is one of the many reasons I am supporting her and advising her campaign.

In my view, she is by far the best prepared of all the candidates to lead our country at this difficult and dangerous time overseas.

Nicholas Burns, a professor at the Harvard Kennedy School and a former under secretary of State who served presidents of both parties during a 27-year diplomatic career, is a visiting fellow at Stanford.