The Thad Cochran Watch is over. The senior U.S. Senator of Mississippi is running for reelection.

The announcement ends months of speculation and squashes potential campaigns for all who have been mentioned except one. Cochran will face state Senator Chris McDaniel in the Republican primary.

There’s no reason to think any other credible Republican will challenge Cochran.

Democrats now have a decision to make: Do they run and full bore back a candidate or do they swing behind Cochran to ensure McDaniel does not win?