The political landscape of the United States has clearly shifted in the Democratic direction, and in most states, a greater proportion of state residents identified as Democrats or said they leaned to the Democratic Party in 2008 than identified as Republicans or leaned Republican.
As recently as 2002, a majority of states were Republican in orientation. By 2005, movement in the Democratic direction was becoming apparent, and this continued in 2006. That dramatic turnaround is clearly an outgrowth of Americans' dissatisfaction with the way the Republicans (in particular, President George W. Bush) governed the country.
With Democratic support at the national level the highest in more than two decades and growing each of the last five years, Republican prospects for significant gains in power in the near term do not appear great. But the recent data do show that party support can change rather dramatically in a relatively short period of time.