Gallup's Bottom line:
Voters' anti-incumbent mood is like nothing Gallup has seen in the past four midterm election cycles. While that could have a negative impact on incumbents from both parties, the greater exposure of the Democrats by virtue of their majority status means greater risk for their candidates. Additionally, both parties have seen their majority control of Congress wiped out in midterm elections with less anti-incumbent fervor than is seen today. Simply put, the party in power seems to take the brunt of voters' wrath in these situations. Gallup's latest generic ballot readings on the vote for Congress, in which support for Democratic candidates is precariously low for that party, point to a similar conclusion.
Read the whole thing and as you do, keep your eye on the Independents.