So … this happened:

Yikes. More from the Washington Examiner:

Sen. John McCain, R-Ariz., on Wednesday accused Sen. Rand Paul, R-Ky., of “working for Vladimir Putin” after Paul blocked consideration of a treaty that would allow Montenegro into the United Nations.

McCain tried to call up the treaty and warned that anyone blocking it would be helping Russia maintain its influence over the small country across the Adriatic Sea from Italy.

“If there’s objection, you are achieving the objectives of Vladimir Putin,” McCain warned. “If they object, they are now carrying out the desires and ambitions of Vladimir Putin, and I do not say that lightly.”

What to make of this? Initial reactions are all over the map:

This could get ugly …

Editor’s note: This post has been updated with additional tweets and text.