WASHINGTON -- Donald Trump is a strange standard-bearer for Republicans. He espouses few of the party's traditional positions and disavows most of its icons. Almost every important conservative publication -- National Review, The Weekly Standard, Commentary -- opposes him, as do most leading conservative pundits, from George Will to David Brooks to Bret Stephens.

Of the five previous Republican nominees for president, three will not publicly affirm that they would vote for Trump and I would bet that a fourth (John McCain) will not in the privacy of the voting booth. And yet, amazingly, in polls, Trump has received around the same level of support from Republicans as previous GOP nominees -- so far. The election might well hinge on one simple issue -- whether Republicans prove to be rational or tribal.

The last time so many Republican leaders defected was in 1964, and Barry Goldwater was wiped out in a landslide. But polarization is so intense in the United States today that a cardboard cutout with an "R" on it would get about 43 percent of the vote, and one with a "D" would get about the same.

For months now, many conservative intellectuals have hoped that the campaign would reveal that Trump was neither Republican nor qualified. It has, on several occasions, most recently at Monday's debate. Public opinion polls showed that Hillary Clinton won by a huge margin. But when Republican and Republican-leaning likely voters were asked in an NBC News poll whether the debate had improved their opinion of Clinton, only 4 percent said yes.

When the same group was asked whether it had worsened their impression of Trump, just 6 percent agreed. (Those numbers were 50 percent and 46 percent, respectively, among Democrats and Democratic-leaners.) Watching the same lopsided debate, people on both sides simply reaffirmed their pre-debate perspectives on the candidate.

These dynamics have reminded me of Jonathan Haidt's seminal book, "The Righteous Mind." Haidt, a social psychologist, uses exhaustive evidence to explain that our political preferences are not the product of careful analytic reasoning. Instead, they spring from a combination of moral intuition (instinct) and a tribal affiliation with people who we believe share these instincts. We use reason, facts and analysis to affirm our gut decisions.

If you think this is true of other people and not you, consider the example of Peter Thiel, a billionaire technology entrepreneur and investor who co-founded PayPal and funded Facebook. He is an extremely intelligent and well-read person, with mostly libertarian views. He strongly supports Trump, for a truly bizarre reason. He asserts that Trump's most significant statement during this campaign, revealing his worldview, was "to declare that government health care can work." He quoted Trump praising the Scottish and Canadian systems -- one a nationalized system, the other a single-payer network -- as proof of his remarkable willingness to think heretically and challenge Republican dogmas about government.

Now, another interpretation of Trump's remark would be that it was a stray comment, thrown off the top of his head, signifying almost nothing. Remember that Trump has taken five different positions on abortion in three days. NBC News calculates that he has changed his position 124 times on 20 major issues since the campaign began. In Monday's debate, he took two contradictory positions on the "no first use" policy of nuclear weapons in 30 seconds.

And most important, after that off-hand reference, Trump backed down from his support for government health care, instead only reciting Republican orthodoxy about the evils of Obamacare. So an intelligent libertarian has chosen to support a man whose main -- and utterly consistent -- public policy positions are anti-free trade and anti-immigration and who has promised to appoint socially conservative judges to the Supreme Court because he is convinced that Trump is actually a closet admirer of Britain's nationalized health care system! I cannot think of a better example of Haidt's thesis that we come to a decision first and reason our way to it afterward.

Paul Ryan has managed similar acrobatics. Ryan is opposed to all Trump's major policy proposals -- the wall, mass deportations, ending birthright citizenship, unilateral tariffs against China, renegotiating NAFTA, total opposition to the Trans-Pacific Partnership -- and has even publicly condemned many of them. And yet, he explains that Trump is his man.

The signs to look for are whether Trump is losing any support among Republicans. That would indicate that politics is about more than tribal loyalty to a team. It would be heartening on many levels. After all, Democracy depends on the ability to look at evidence and argument, to use reason and judgment, and to take seriously our roles as citizens of a great republic.

<FAREED ZAKARIA>