...The responses from GOP senators were, as is typical of the upper chamber, somewhat more cautious than from other Republicans. Some reportedly even said they were declining to comment because they might one day be jurors at an impeachment trial in the Senate (which is a pretty amazing response).

But even considering that, the non-responses are unusual and remarkable. The GOP response de rigueur before midweek was to ignore questions about whether Trump did anything wrong and emphasize that his concerns about Joe and Hunter Biden’s actions in Ukraine were warranted — suggesting the whole thing was just about getting Ukraine to root out actual, real corruption.

That seemed to shift Thursday though, especially in the Senate, where Republicans seemed genuinely skittish about mounting anything like real defense of Trump. A few of them have criticized Trump for his Ukraine interference, including Sens. Mitt Romney (R-Utah), Ben Sasse (R-Neb.) and Patrick J. Toomey (R-Pa.), the last of whom called Trump’s call with Ukraine’s president “inappropriate” but not impeachable. Yet the rest of them don’t really seem to comfortable firmly taking the other side: that this is a nothingburger.

It’s difficult not to read that as evidence of genuine concern about what lies ahead. Even if Republicans truly think nothing bad happened — or that it wasn’t bad enough to cause the party problems — there is so much we don’t know at this point. And judging by Trump’s behaviors in the past, do any of them really want to gamble that what eventually comes out won’t make their initial defenses look foolish? We have a president who on that call with Ukrainian President Volodymyr Zelensky talked about all the United States does for Ukraine, and then immediately launched into asking for a “favor,” before pushing for two specific investigations that carry obvious domestic political benefits for him. Even if there may never be an explicit quid pro quo, Trump was unquestionably asking for foreign assistance in his reelection campaign....