“Everyone is getting a little shaky at this point,” said Brendan Buck, who was counselor to former House speaker Paul D. Ryan (R-Wis.). “Members have gotten out on a limb with this president many times only to have it be cut off by the president. They know he’s erratic, and this is a completely unsteady and developing situation.”…

Former Republican senator Jeff Flake, a Trump antagonist, said his former colleagues believe the foreign leader interactions under investigation in the House represent “new territory” compared with past challenges, including the Russia investigation.

“There is a concern that he’ll get through it and he’ll exact revenge on those who didn’t stand with him,” Flake said. “There is no love for the president among Senate Republicans, and they aspire to do more than answer questions about his every tweet and issue. But they know this is the president’s party and the bargain’s been made.”…

This is not the first such crossroads, of course. Republicans largely stood behind Trump in 2016 after the release of the “Access Hollywood” tape on which he bragged of sexual assault, as well as during the darkest days of the Russia investigation and in the wake of racist comments.