As so many Republicans desperately wish Obama ends up as a OTP (One term president), I thought it's a good time to look over the one term presidents of the 20th century and find out why they lost re-election.
1. George H.W. Bush (R). First of all, he lost to Clinton, one of America's more popular presidents. Clinton is the only president to have no recession during his presidency. Bush's problem related to a bad economy, violence in inner cities, and high deficit spending.
2. Jimmy Carter (D) Carter lost to perhaps the most beloved Republican President - Ronald Reagan. Carter most likely lost due to military failings (hostage in Iran,) plus high inflation. Even the Democrats were worried about him - as a Kennedy opposed him in the primary.
3. Gerald Ford. (R) He lost in part because he was never elected. He was appointed VP by Nixon, perhaps the least popular president. Like Carter, he had issues with inflation and the economy.
4. Herbert Hoover. (R) He lost to Franklin D. Roosevelt, again a very popular person (only president to serve 3 terms). The Great Depression started on his watch - within months of his election and he could not get out of it.
5. William Taft (R) He alienated members of his own party. His predecessor was Teddy Roosevelt who got so mad at Taft Teddy left the GOP and started his own party.
During the 20th century, 52 years were under Republican presidents and 48 were under Democrat presidents. The first thing to note is that most of the one term presidents in the 20th century were Republicans, while the office itself was pretty much split 50:50 between the parties.. Four to one ratio is important. Apparently, Americans elect more Republicans, but regret it enough to balance things out.
Three things tend to stick up. One term presidents are created by 1) Bad economies. 2) star competition and 3) a dis-unified base. Obama has a poor economy to fight against. He does not have a star competitor nor does he have a problem with his base. As long as the economy does not get worse, Obama is going to be re-elected. The question is, what happens if the economy gets worse. Which is why many (if not most people) think the GOP may be trying to kill the economy (at least Floridians think so - source)
It is also important to note that our data may be flawed. We only have a single one term Democrat to look at, vs 3 Republicans. One data point is not very informative. It is possible that what kills a Republican president won't kill a Democrat President and vice versa. For example, Republicans care more about family values. A Republican may not be able to win as pro-choice, but clearly Democrats do all the time.
In general, the people look to a Democrat to fix the economy and a Republican to save them from enemies. Mommy vs Daddy, prosperity vs war. If that is the case, then a bad economy will kill a Republican, but it takes a bad foreign situation to kill a Democrat. Some people think Carter's failure to resolve the Iranian hostage situation may be more responsible for his defeat than his failure to fix inflation. This was compounded by dissension in the ranks, Carter faced a primary challenge against a Kennedy. Obama has no such competition.
Obama has consistently outperformed in foreign affairs. He is ending two wars on the same schedule his predecessor set up, started and won another one (Libya) with far fewer American casualties, and taken out multiple terrorists (including Bin Laden) that have been plaguing America for decades. Obama has no foreign enemies issue.
Obama has no real competition within the DNC. While some Democrats are upset with him and wish he had done/could do more, the rank and file support him This compares to a very divided GOP that ignores their best declared candidates (Huntsman), barely supports their one 'acceptable' candidate (Romney), while continuously obsessing about outrageous people (Palin, Bachmann, Paul, Perry, Cain) that say preposterous things.
Is it possible for Obama to lose? Yes. A worsening economy may do that. But if things stay the same or get better, Obama will win. Easily.