Mott the Hoople
Sweet Jane
I've read analysis on the Cook Political Report that as few as 700 State Legislative seats could flip this election cycle, with the possibility going up as high as 1,000 seats. In addition to that, there are twelve (!) governorships for which Democrats are in prime position to flip, which would give them a majority of state governorships.
As the saying goes, all politics are local, and if this were to happen...a big if...then it would be a significant strategic gain for the Democratic party....that's still a big if.