Andrew argues that the races today are not about Obama. Who said they were? They're about Democrats and Republicans. They're about whose base is more energized.
If Hoffman wins in NY-23, I assume that makes the squishier Republicans swallow hard and wonder if they might not be vulnerable to a challenge from their party's right wing--not to mention a bunch of Blue Dogs who will be looking at the Republicans and independents in their own districts. If two states with Democratic governors lose them, that signals that the Republicans can move motivated bodies to the polls . . . and while voters may be saying they like Obama as much as ever, they're also saying that they think their taxes are too high and government spending is out of control, issues that polled way higher than "Obama issues" like health care.
All of this makes it tempting to tack right. Because here's the thing: 2010 won't be about Obama either. Oh, his performance over the next year will matter--but he's not going to get that surge of voters out to the polls for house and senate races. The Blue Dogs who are up for election in 2010 aren't worried about Obama, or his voters. They're worried about their own political fates.