Major shift in Party Affiliation

By contrast, the percentage of self-described political independents has steadily climbed, on a monthly basis, from 30% last December to 39% in April. Taking an average of surveys conducted this year, 36% say they are independents, 35% are Democrats, while 23% are Republicans. On an annual basis, the only previous year when independent identification has been this high was in 1992 when Ross Perot ran a popular independent candidacy.

As has been the case in recent years, more independents "lean" Democratic than Republican (17% vs. 12%). Yet an increasing share of independents describe their views as conservative; in surveys conducted this year, 33% of independents say they are conservatives, up from 28% in 2007 and 26% in 2005. Again, this ideological change is at least in part a consequence of former Republicans moving into the ranks of independents.

http://pewresearch.org/pubs/1229/political-values-core-attitudes-trends-2009