“Impeachment would be a mistake,” Sen. Lamar Alexander of Tennessee, a Republican bellwether on the issue, said in a statement Wednesday. He said while it was “inappropriate” for Trump to have prodded foreign governments to investigate his political opponents, next year’s election is “the right way to decide who should be president.”

Alexander, 79, is retiring after four decades in politics. He’s respected by both parties as an independent voice who’s already taken on Trump, including opposing his efforts to unilaterally spend money on building a Mexican border wall…

The GOP’s four senators and 17 House members who have announced they are not seeking reelection next year are largely loyalists with little history of bucking party leaders. Political consultants and academics consider past voting records and ideology key indicators of whether lame-duck lawmakers will abandon their party.

“They’re sort of off the leash there, they can bark as much as they want” with their rhetoric, said Michael Romano, a political science professor at Virginia’s Shenandoah University who’s studied lame-duck lawmakers. “Whether or not that translates into an actual vote is kind of mitigated by ideology, a lot.”