I feel like the power of the off-year versus 4/8/12 presidential year is so ignored by both this forum and the media, it's silly.
Democrats have to watch their asses way more in 2010 than in 2012. Part of the reason why so much Democratic obstructionism is occurring. Not that anyone cares beyond their ideological preferences.
I don't think the higher turnout in a Presidential election year necessarily helps Democrats that much in Congressional races. Historically, there seems to be no correlation with one party or the other doing better in Prez years vs. midterm years.
Now, it is possible that black turnout might be lower in 2010 but higher again in 2012, as well as youth turnout. To that extent, you may be on to something. But we also can't assume it'll be dramatically lower in 2010 either as opposed to turnout among other groups.