Last time, in case anyone is still confused – the “tea party” is just the rump Republican base with tricorne hats on. These are not new voters:
There are now more Republican-leaning independents among independents in general than there were in 2006, but the main reason is that the number of actual Republicans has significantly declined.
OK, so why has the weight of Republican-leaning independents among independents increased? This is a tricky question, but possibly the most important single factor is that there has been an actual decrease in the number of straight Republican identifiers among registered voters (down 2 points) which has produced a concomitant increase in the number of Republican-leaning independents over the 2006-2010 time period. It’s also interesting to note that that this switch can account for most of the 3 point overall increase in independents over the time period.