Who had the worst week in Washington? Sen. Mitch McConnell

Sen. Mitch McConnell is nothing if not careful and crafty. Which is what makes what happened on the Senate floor Wednesday night all the more remarkable.

At issue was legislation to raise the debt ceiling — essentially paying the nation’s credit card — without any sort of sweeteners attached to it to entice Republicans. The House had passed the measure Tuesday with just 28 Republicans voting for it.

McConnell, R-Ky., the Senate minority leader, quite clearly had no interest in walking the plank — or forcing his GOP colleagues to do the same — and was content to let the debt ceiling pass on a simple majority vote. That would allow every Republican to vote against it, keeping their fiscal conservative credentials intact with primary challenges looming. (McConnell faces a conservative Louisville businessman, Matt Bevin, in a May primary.)

Then Ted Cruz happened. The tea-party-inspired senator from Texas refused to let the debt ceiling be raised by a simple majority, forcing McConnell to round up five Republicans to secure the 60 votes needed to end debate on the measure.

Then the centrist revolt happened. People like Republican Sens. Lisa Murkowski (Alaska) and Susan Collins (Maine), typically reliable votes in these sorts of circumstances, pushed McConnell to throw his lot in with them or face a vote shortage. Hand-wringing ensued. The vote was held open for the better part of an hour until McConnell and Senate Minority Whip John Cornyn (Texas) simultaneously voted “aye” — a vote neither man wanted to take.

McConnell is still a favorite in his primary against Bevin, but the minority leader’s vote gives his rival some fresh material to work with.

McConnell, for forgetting you always need a plan B — and a plan C — on the Senate floor, you had the worst week in Washington. Congrats, or something.

Cillizza covers the White House for The Washington Post and writes The Fix, its politics blog.