It’s a prospect that may seem far-fetched. Senate Republican officials say the party still foresees an almost entirely partisan outcome in a potential impeachment trial. And Republicans — especially those up for election in 2020 — have long been afraid of losing Trump’s base if he turns on them. They’ve rarely defected from the president in large numbers for key votes.

But the landscape could shift quickly if fresh details emerge that help Democrats make their case that Trump must go, said Michael Steel, a longtime GOP operative and aide to former House Speaker John Boehner.

“If the Democrats are able to make an argument that’s clear and captures the public imagination … then you start thinking more seriously about what a Senate trial could look like and whether you could get to that possibility,” Steel said of a scenario in which enough GOP senators defect to remove Trump…

“President Trump really goes after anyone who is anything less than completely supportive. The way he’s gone back after Sen. Romney is inappropriate and disgraceful,” Coons said. “If I were a Republican senator, I would make a pretty tough but prompt assessment that history will judge harshly those who do not show some independence from this president.”