If you had to point to a single voter group that cost Democrats the 2010 election cycle it was independents. Not only did Republicans win them in pretty much every key race this year, they did it by wide margins.
Here's some good news for Democrats though: our early 2012 cycle polling suggests the strong GOP lean of independent voters this year was more of a blip on the radar screen than a sign of things to come. Since the election we've polled 51 different possible Senate/Governor contests for 2012 and across all those different permutations Democrats are leading by an average of 6 points. And when you look at the 48 prospective Presidential match ups we've tested that spread expands even further to an average lead of 11 points for Barack Obama with independents.
This speaks to a couple things. The biggest is that it's yet another reminder that the folks who turned out this year bear little resemblance to a Presidential year electorate. Conservative leaning independents who tend to vote Republican were much more inspired to vote this year than more centrist independents who usually support Democrats. If the moderates come back out next time, as they probably will, that in and of itself is going to be a big boost for Democratic candidates within that voter group.
The other thing it's a reminder of is that even though independents voted for Republicans this year it doesn't mean they like the GOP. Our November national poll found a 17/60 approval spread for the Republicans in Congress with independents. A poll we did earlier in the year found that only 18% of independents generally though the GOP was going in the right direction, while 49% thought they were off on the wrong track. Republicans are going to have to show independent voters something different than they have been if they hope to win their votes again in 2012.
I think you're a lot more likely to see independent voters give a single digit edge to one party or the other in 2012 than the sort of landslide margins they tended to give Republicans in the key races we were polling in 2010.