Mr. Chen lamented that too many in the party were still pursuing a Trump-first approach to politics: “Many Republicans are more focused on talking about him than about what’s next, and that’s a very dangerous place to be,” he said.

In recent weeks, the party has been so submerged in internal conflict, and so captive to its fear of Mr. Trump, that it has delivered only a halting and partial critique of Mr. Biden’s signature initiatives, including his request that Congress spend $1.9 trillion to fight the coronavirus pandemic and revive the economy. Mr. Trump has complicated Republicans’ quest to develop their own policy message: his contempt for fiscal restraint and his 11th-hour endorsement in December of $2,000 cash payments as a stimulus measure have left congressional Republicans with only weak standing to oppose Mr. Biden’s biggest plans.

Mr. Trump’s tenure as an agent of political chaos is almost certainly not over. The former president and his advisers have already made plain that they intend to use the 2022 midterm elections as an opportunity to reward allies and mete out revenge to those who crossed Mr. Trump. And hanging over the party is the possibility of another run for the White House in three years.