There's naturally an obsession among political folk about monitoring the President's approval ratings, with some recent national and state surveys showing a sag. But it's worth remembering that politics is not necessarily a zero-sum game in which weaknesses automatically create strength for the opposition, particularly in a period of public unhappiness, and particularly when memories are fresh of how people felt when the opposition was in power.

Moreover, at the state level anti-incumbency feelings don't always hit the party in power in Washington.

There's a good example of this phenomenon in a new PPP poll from Minnesota. It shows the President's approval/disapproval rating deteriorating from 60/30 in April to 54/39 now. But that hasn't translated into any measurable Republican gains. MN's own Republican governor, Tim Pawlenty, one of the most-cited possibilities for the GOP presidential nomination in 2012, has suffered his own slide in approval ratings, down into negative territory, from 46/44 to 44/48. And more to the point, a 2012 trial heat shows Obama thumping Pawlenty in his own state 51-40.

Is Pawlenty's weakness a function of the "Republican brand" or of his own incumbency? Hard to say. But the same poll shows Sarah Palin, who recently decided to get rid of the handicap of governing, with a 39/53 approval ratio, and losing to Obama in a 2012 trial heat by 56-35.

So if you're into polls, it pays to keep an eye on everyone's approval ratings, and on actual electoral matchups, not just Barack Obama's numbers.