The closer it gets to election day, the better it is looking for Democrats. Nearly every pundit is now predicting that Democrats will again seize the Senate, and some are starting to predict the Democrats could even finish with a House majority.
The latter will be difficult, thanks to some rather effective gerrymandering done by Republicans on the state level in 2010 -- but it is doable, especially considering the GOP residential candidate (who seems to have no coattails).
The charts above would tend to show Democrats have a real chance this year. About 46% of voters blame Republicans for the do-nothing Congress, while only 7% blame Democrats. In addition, both congressional party officials and the parties in general show that Democrats are viewed more favorably than Republicans.
These charts were made from information in a very recent Economist / YouGov Poll -- done between August 19th and 23rd of a random national sample of 1,300 voters, with a 4 point margin of error.