That's a pretty mediocre showing for Obama in PA. I thought Obama would be leading by more than that, especially since he has a lead in OH and a solid lead in MI.
President Obama, should his approval numbers be where they are a year from now, will need to campaign to win. My predictive model suggests that an incumbent Governor, Senator, or probably an at-large Representative (this is an adaptation from Nate Silver) gains a vote share of roughly 6% on the average. This applies just the same to pols whose approval is in the 30s as it does for incumbents with approvals in the 60s. Practically all incumbents facing a challenge do some active campaigning, and although there are some whose approval is in the high 40s and still lose, there are few. They can get votes only in their own states in a gubernatorial or senatorial election, so don't expect Debbie Stabenow (D, MI) to be looking for votes in Indiana or Ohio in 2012.
Losing with an approval rating in the high forties implies that
(1) a scandal breaks late
(2) the local economy goes very bad, and the politician gets some of the blame
(3) the candidate runs an incredibly-bad campaign
(4) the opponent is unusually strong as a challenger
(5) the candidate is excessively linked to an unpopular President
Politicians whose approval ratings are in the 20s either don't normally run for re-election
or else get defeated in their party's primaries. Sure, George Allen (R, VA, 2006) barely lost despite having an approval rating of 51% at the start pf the campaign season, but he blundered badly, he was too closely linked to a President going unpopular rapidly, and his opponent was unusually strong for a challenger.
Start by assuming that the incumbent has previously been elected, so there is little question of whether he knows how to campaign, knows enough of the demographics of the state to go to the right places, and has a campaign apparatus either already set up or has people who can set one up. Well, that didn't apply to Gerald Ford in 1976 -- and it showed.
Most of the losing incumbents begin with approvals in the low 40s or even the 20s. Most gain some (let us say Santorum in 2006 or Corzine in 2009) -- but not enough to win.
I figure that the effect is about as strong for an incumbent President in any state, but only if his approval rating is in the forties. If it is appreciably lower, then he probably has little chance to win the state and isn't going to invest much effort in it. So if the polls generally say that his approval rating is in the thirties in either Indiana or Missouri, then don't count him to put much effort into the state and don't expect his campaign apparatus to pay for much advertising or a get-out-the-vote campaign for long. 45% of the vote at the end is as worthless as 15% of the vote. But what if the early polls tempt him with 41% approval? Campaigning there and having a campaign apparatus might be tempting. Indiana or Missouri might then be tempting if only as places in which to waste the Other Side's resources if one has money to burn.
I expect the effect to be muted on the high side as well. If one sees a state going firmly for one, then there might be wiser places in which to invest campaign efforts and advertising. If the President's approval rating in California is 53%, then expect him to make few campaign appearances there. Maybe national effects might drive the final vote share to 57% or so, but winning 57%-43% in California is no better than winning 53%-47%. So one cuts off the efforts when it looks as if one is about to win or lose by about a 10% margin fairly early and moves resources (including campaign staff and advertising) where it can do some good. One might do efforts to bring a 52-48 margin up to a 56-44 margin, but beyond that any further gains are the result of national effects.
I'm going to suggest that Barack Obama knew enough to encourage people who worked on his campaign in California to relocate to such a 'dicier' state as Nevada (pardon the bad pun) or Colorado, and his enthusiasts in Texas to relocate to Colorado, Florida, or Missouri. He was going to win in California and lose Texas, but he understood that winning Colorado, Florida, or Missouri sealed everything. I expect him to repeat his efforts that either succeeded or came close to succeeding in his first Presidential election in 2012.
Because it isn't wise to pile up votes in a sure-thing state or to try to win over a sure-loss state, don't expect much campaign advertising in Rhode Island or Wyoming.
