Rather, it’s rank-and-file Republican senators up for reelection in solidly red states, like Bill Cassidy from Louisiana or Jim Inhofe from Oklahoma, whom you should watch. If they waver, that will signal that Trump’s days are numbered. Of course, the rub is that neither have spoken out against Trump — in fact, they’ve stuck by him — but that’s the point. If Republicans do abandon Trump over impeachment, it will be because of the senators least likely to strike out against Trump balked.

Each new development potentially changes the calculus, too. For instance, last Tuesday, the Senate unanimously passed a nonbinding resolution calling on the Trump administration to release the whistleblower complaint that alleged the president had tried to coerce the Ukranian president to investigate Democratic front-runner and former Vice President Joe Biden. The resolution signaled a surprising bipartisan willingness to let more information out. But by Thursday, after the whistleblower’s complaint went public, most Republicans had already rallied around talking points that questioned the motivations and veracity of the whistleblower, instead of criticizing Trump. The short-lived moment for a cascade passed almost as quickly as it had come.

But if you’re looking for another moment when Republicans might break with Trump, look for an event like last Tuesday. Moments like that can create uncertainty and situations where the ground can shift quickly. For most congressional Republicans, this is no doubt a frustrating state of affairs. Few presumably relish defending Trump against the increasingly indefensible. But this is where the party is currently stuck.