The quandary, some Republicans acknowledge, is that the party’s leaders are constrained from fully grappling with the damage Mr. Trump inflicted with those voters, because he remains popular with the party’s core supporters and with the conservatives who will dominate the caucus even more in the next Congress…

“There has been close to no introspection in the G.O.P. conference and really no coming to grips with the shifting demographics that get to why we lost those seats,” said Representative Elise Stefanik, an upstate New York Republican who is planning to repurpose her political action committee to help Republican women win primaries in 2020. “I’m very frustrated and I know other members are frustrated.”…

Or as Representative Ryan Costello of Pennsylvania, who is also retiring, put it: “It’s clear to me why we lost 40 seats; it was a referendum on the president, but that’s an extremely difficult proclamation for people to make because if they were to say that they’d get the wrath of the president.”