Do you have some evidence for that opinion? I have seen none, not that there couldn't be any. Everything that I have read indicates that independents and/or moderates shifted their votes in 2006 when the rats took Congress, 2008 when the rats increased their majorities, and our way taking back the House in 2010.
I've posted stories about the exit poll results using the keyword format 20XXexitpoll. Just substitute 06, 08 or 10 for XX in that keyword.
We continually hear the same story over and over that the Republicans lost their way and that is why they lost in 08, as though the Republicans deserved to be thrown out and it makes more sense to vote for Democrats.
The only way that makes sense if the same people who voted Republican before either voted, Democrat in 08, stayed home or voted "third party".