Republicans are going to have a wave election in 2010 just like democrats did in 2006. But Public Policy Polling notices that the character of the wave is completely different. The Democrats won in 2006 by winning over a lot of Bush voters. Republicans this year aren't winning over Obama voters -- they're just mobilizing their base while Democrats sit at home:
The Democrats' big win in 2006 was not driven by the enthusiasm gap, but because a lot of people who had voted for George W. Bush in 2004 switched over to supporting Democratic candidates. According to the 2006 exit poll the electorate that year was actually more heavy on Bush voters than the 2004 electorate that reelected Bush. 49% were Bush voters to only 43% who were Kerry voters, compared to Bush's 51-48 popular vote victory in 2004.
The reason Democrats won even though the electorate disproportionately consisted of Bush voters was that 15% of those Bush voters cast their ballots for a Democrat, a pretty large amount of crossover.
There aren't nearly that many Obama voters leaning toward the Republicans this year. Our last national generic ballot survey found only 8% of people who voted for the President in 2008 were planning to support the GOP this year. But those surveyed represented an electorate that favored Barack Obama by only a point, 46-45, and because of that the generic ballot was tied despite the small number of voters crossing over.
The big 2006 Democratic win was about voters abandoning the GOP. If Republicans have a big win in 2010 it's mostly going to be about Democrats staying home.
PPP also notes hat Obama might be in decent shape in 2012 if he can get his base to turn out again. Of course, the economy will determine that.