Peter Feaver, a Duke University political scientist who served as a National Security Council aide to President George W. Bush, told me Trump’s accommodation of Russia is unlikely to precipitate any sort of lasting change. He argued that there is still enough skepticism in the party about Trump’s policy toward Russia—and the country’s international role more broadly—that the president risks eruptions of discontent that force him to retreat, like those he confronted over his withdrawal from Syria. Even inside the administration, he noted, most foreign-policy experts remain dubious of Putin, which helps explain why the administration’s actions toward Russia have sometimes been tougher than Trump’s accommodating rhetoric.

“No one knows for sure, including the president,” how far he can push the party, Feaver said. “The president is wandering around a mine field and doesn’t always know when he is going to step on a mine.”

That may be true. But the willingness of more congressional Republicans to amplify widely discredited arguments against Ukraine—despite repeated warnings from conservative national-security professionals that they are advancing Russian propaganda in the process—suggests that their tolerance for Trump’s repositioning of the party on Russia is only growing.

As Fontaine told me, historically, “one of the reasons people were attracted to the Republicans was because they were the party skeptical of the regime in Moscow.” That’s one more Republican tradition Trump has tossed onto the ash heap of history.