As soon as Sasse sat down, McConnell lit into him, criticizing him for working with the Senate Conservatives Fund (SCF) as well as for posting a viral YouTube video in which he demanded “every Republican in Washington, starting with Minority Leader Mitch McConnell, to show some actual leadership.”

Republicans in Washington familiar with these kinds of sessions say the Kentucky Republican’s specialty is long, tension-filled pauses. But even for McConnell, this was awkward. Josh Holmes, McConnell’s top political hand, privately told friends afterward it was the most uncomfortable meeting he’d been in.

Following the initial exchange came a series of questions about exactly when Sasse had first interacted with Matt Hoskins, the hard-charging executive director of SCF working to elect McConnell’s primary challenger, Matt Bevin, in Kentucky.

Sasse’s answers, several Republicans familiar with the episode say, did nothing to mitigate the minority leader’s anger.

As he walked out of the room, Sasse turned to Holmes — “That didn’t go well!”