The change of heart came after a recent poll the DSCC conducted, but not because it showed Judd was incapable of competing with McConnell, rather that Grimes performed better than Judd and gave Democrats the best chance at victory.
As late as last week, the wheels were already very much in motion at the DSCC in planning a Judd Senate candidacy. While those plans have not been scrapped, there is definitely a re-evaluation happening. Our sources tell LEO that while the DSCC felt that Judd could compete with McConnell, one of Judd’s strongest assets would be her ability to raise money on par with McConnell and tie up Republican campaign spending (both McConnell’s and the NRSC’s) in that race. However, their recent polling suggests the 2014 race is very much winnable, with McConnell so vulnerable that Democrats need to make their priority finding the candidate with the best chance of winning.
Then again, they are not entirely sure at this point that Grimes would even entertain a run against McConnell, as she has plenty of other races in the next three years that she could choose to run in, most of which would not be nearly as difficult as the 2014 Senate race.
As I've said before, this is an empirical opportunity to test the "Better Dems vs More Dems" theory of taking back over Congress. If Grimes can beat McConnell, even though Judd is far more liberal, is it worth backing Grimes to get rid of Mitch McConnell?
On the other hand, a Democrat who can win a statewide race and still be a viable candidate for Congress is a rare opportunity. On the gripping hand, Grimes may simply run for Dinosaur Steve's seat as Governor, something in the long run I would much rather have as a Kentucky voter.
We'll see how this shakes out. If Grimes turns the DSCC down, getting behind Judd may be the way forward.