Hillary Clinton clearly believes that she enjoys a decided advantage over Donald Trump when it comes to foreign policy. Her speech today in San Diego launched what will clearly be a sustained attack on Trump’s qualifications as commander-in-chief. Citing his support for torturing the families of terrorists, his loose talk about using nuclear weapons on ISIS, and his calls for walking away from NATO and other allies, Clinton argued that Trump’s ideas about foreign policy are “dangerously incoherent.” His main tools of global statecraft, she said, would include bragging, mocking, and composing nasty tweets. In short, Clinton’s central theme is that Trump is simply “not up to the job” of president and if elected, Trump would lead America down a “truly dark path.”

Though most of Clinton’s attacks by this point have already been well rehearsed, the account against Trump is nonetheless devastating. Or at least the attack would be devastating to some other candidate in some other election year. This year, however, things look very different.

The most recent Washington Post/​ABC News survey found Americans almost evenly divided over whether Hillary Clinton or Donald Trump would do a better job keeping the country safe, dealing with terrorism, and dealing with international trade. Can these numbers be real? Can almost half of the American public honestly prefer a man who clearly has given so little thought to international affairs over a woman who has traveled the world, served as a United States senator, and spent four years as Secretary of State? The surprising answer is yes.

There are three things keeping Clinton from winning the foreign policy debate.

The first dynamic fueling this situation is partisan polarization. As research has begun to make clear, the United States now suffers from an extreme case of “partyism.” Republicans and Democrats now dislike each other so much that they oppose each other instinctively regardless of the facts – witness how much Republicans still think President Obama is a Muslim. On the question of keeping the country safe, the Post/​ABC survey found that 84% of Democrats think Clinton will do a better job but 83% of Republicans think Trump will do a better job. The fact that Trump commands such partisan loyalty despite his clear lack of knowledge and experience illustrates just how powerful a force partisan polarization has become in the United States. This alone will make it very difficult for Clinton’s (or anyone else’s) substantive arguments to gain any traction.

The second force at work is the appeal of Trump’s foreign policy views. Whatever his deficits on paper, on the campaign trail Trump’s “America First” rhetoric aligns more closely with public preferences than Clinton’s liberal interventionism does. Clinton denounces Trump for unrealistic and dangerous talk about allies, trade deals, and refugees, arguments that resonate with pundits and party leaders inside the Beltway. Trump, meanwhile, scores points with the public for understanding that for most Americans the best foreign policies are those that improve things at home. A recent Pew survey, for example, found that 57% of the public thinks the United States should deal with its own problems and let other countries deal with theirs as best they can. That same survey found that more Americans now believe American involvement in the global economy is a bad thing than a good thing. And a whopping 70% of the public wants the next president to focus on domestic policy; just 17% want him or her to focus on foreign policy. In treating foreign policy as an extension of domestic policy, Trump has plugged into a deep reservoir of public concern that the White House has allowed foreign policy to distract the United States from more pressing matters.

Finally, Clinton’s own weaknesses on foreign policy are helping buoy Trump’s case. Her foreign policy record includes a long list of decisions that challenge her narrative of superior judgment and temperament. Bernie Sanders has paved the way for Trump on this score, pressing Clinton repeatedly on her decision to vote in support of the 2003 invasion of Iraq when she was in the Senate and criticizing her for the mishandling of the Libyan intervention. Nor has Trump been shy about following Sanders’ lead. At a rally earlier this month Trump called Clinton “trigger happy” and said, “Her decisions in Iraq, Syria, Egypt, Libya have cost trillions of dollars, thousands of lives and have totally unleashed ISIS.” Nor is that just campaign rhetoric. From Afghanistan to the Libyan intervention to the Syrian civil war, Clinton has repeatedly staked out aggressive interventionist positions that go beyond what most of the public supports, leaving her wide open to Trump’s counterattacks.

In the end, Clinton is correct: Trump clearly does not possess the qualifications or the temperament to lead the United States. Unfortunately, Clinton’s critique leaves voters with only a “less bad” alternative to Trump rather than with a compelling vision of America’s role in the world. And with the approval ratings of both candidates at historic lows, it is unlikely that either will manage to score a knock out blow on foreign policy in the general election. In fact, with approval ratings of the two candidates at historic lows, it would not be surprising if large numbers of disaffected Democrats and Republicans leaned toward a third party ticket that eschews the aggressive interventionism of Clinton and the belligerent nationalism of Trump.