How's this for a political rule- Since 1916, an incumbent president has never been reelected a second time with a smaller PV percentage than he did the first time. When they're up for reelection, they either win by a bigger margin or they lose.
Some examples:
Eisenhower 1952: 55%
Eisenhower 1956: 57%
Reagan 1980: 50%
Reagan 1984: 58%
Clinton 1992: 43%
Clinton 1996: 49%
You could argue that FDR doesn't fit this trend, since he won by less his third and fourth times running, but his tenure was unprecedented.
So if Obama wins, will he be the first president since Wilson to gain a second term with less support than he did the first time? The polls look like it.
You missed even Dubya, who won by a bigger margin even if he should have been defeated. if we had only known back then the damage that he was doing to America...
Dubya, 2000 48%
Dubya, 2004 51%
If it is any consolation the 3% gain was weak for someone who did much campaigning (Eisenhower didn't campaign much in 1956).
This is a diverse lot. In theory one expects an incumbent President to achieve his promises while convincing some who didn't vote for him the first time that he isn't that bad. He satisfies his original voters or he fails completely -- like Carter or Hoover. If people tire of the agenda, like the third-term-in-all-but-name of Ronald Reagan that the elder Bush tried to win, then incumbency is no asset.
Hoover ran on the economic achievements of his predecessors -- "a car in every garage and a chicken in every pot" in 1928, and had nothing to run on in 1932. Carter made promises of some administrative reforms including zero-based budgeting and didn't get them. To win re-election he had to make fresh promises to win over new constituencies, and such is impossible.
President Obama wins by a larger margin if
(1) significant third-party candidates cut into right-leaning votes at the expense of Mitt Romney. Just take a look at how Virgil Goode does in Virginia. Goode seems to be a good cultural match at least for the Mountain South -- far better than either Obama or Romney. If he runs in Georgia and Missouri he siphons away enough right-leaning votes in those states to flip them to President Obama.
(2) Romney collapses as a candidate. We just haven't seen that yet, and I am not going to call that until I see it.
...Barack Obama was a horrible match for the political culture of much of America and still is. It is hard to imagine any Presidential candidate winning by as large majorities in so many states and losing by as large majorities in so many. He can still win while some of the huge margins by which he won in 2008 get pared (he won by 20% or more in eleven states and by 15% to 20% in six others), he loses by similar margins in states that he lost by 14.9% or more, and campaigns effectively enough in the swing states to win what he must. He could conceivably gain electoral votes while losing some of the huge margins that he won by in California, New York, New Jersey, Connecticut, and Massachusetts.
