Not That far down - Obama has to slip to a 45% approval rate to risk Re-election

(Fivthirtyeight via Race42012).Nate Silver has completed another insightful analysis regarding the effect of President Obama’s Gallup approval ratings on Congressional mid-terms and his re-election chances:

"Barack Obama's approval rating had dropped to 50 percent in the latest Gallup poll...

The thing is, though, that Obama's approval rating haven fallen to 50 percent is not particularly newsworthy. There's no reason that a drop from 51 percent to 50 percent, or from 50 percent to 49 percent, means anything particularly more than a drop from 58 percent to 57 percent, or from 37 percent to 36 percent.

First of all, although I'm on record as being quite pessimistic about what's liable to happen to the Democrats in 2010, odds are that Obama's approval will have to be somewhat worse than 50 percent for the Democrats to lose the House. The relationship between Presidential approval and his party's fate at the midterm elections is quite linear. An approval rating of 50 percent would typically be associated with a loss of about 26 seats.

The Democrats, however, currently have a 78-seat advantage in the House, meaning that it would take a 39-seat loss for them to lose control of the chamber. The over-under for how unpopular Obama would have to be in order to be more likely than not to cost his party those seats is not 50 percent -- it's probably more like 42 percent....

Likewise, Obama can probably afford an approval rating below 50 percent and still be a favorite to win re-election in 2012. George W. Bush won in 2004 with an approval rating of 48 percent, and Harry Truman won in what was considered a huge upset in 1948 with an approval number that had last been tested at 39 percent..

Against Sarah Palin, frankly, Obama could conceivably win re-election with an approval rating well into the 40's and possibly even into the 30's. He'll have less margin of error, potentially, if the GOP nominates someone like Mitt Romney .But again, there's nothing particularly special that happens at 50 percent. Something like 45 percent, which is where Gerald Ford was when he lost to Jimmy Carter by two points in 1976, might be the more relevant number.

A quick-and-dirty probit analysis, based on a dataset and placing slightly more weight on recent elections, puts the breakeven number at 44 percent, and suggests that a President at 50 percent approval is as much as a 90 percent bet to win a second term: