The more I think about it, the more convinced I am that what's motivating Reid and Rockefeller is a simple desire for this whole issue to go away. As was mentioned upthread, they were probably briefed on the NSA program early in its run and didn't object when they had the chance. Now it would seem that EFF vs ATT is in a position to uncover the whole termite nest and they'd rather that didn't happen.
The confidence they feel over the prospect of a Dem ending up in the White House is probably firming up their resolve even more. After all, if the big prize is theirs anyway, why risk any more chips?