Here's my op-ed in The Daily discussing the little-noticed fact that presidents seeking reelection either almost uniformly improve on their original election totals or lose the race (hence, "do better or get out).
A couple of additional thoughts, some recall related:
This rule seems to occur on both the Electoral College and popular vote levels. Only Woodrow Wilson bucked the trend, and if not for the bizarre interaction between California Governor and recall hero Hiram Johnson and 1916 Republican Presidential candidate Charles Evans Hughes we may not even have that one (plus an asterisk for James Madison -- the added some states). Also, Teddy Roosevelt's backing of the recall in 1912 was a factor in the Republican Party split (I'll have to write about that another day -- I think the third term arguments about that race are overrated by historians).
I was surprised that Andrew Jackson actually did worse in the popular vote in 1832 than he did in 1828 -- I always thought of his reelection against the the Great Compromiser (now, that awesome nickname would be seen as an insult) Henry Clay as crushing, but apparently not as big as his original crushing election. Of course FDR did worse in terms 3 and 4, but that's a horse of a different color.
Since other Executives (in both other countries and the US) regularly beat the "do better or get out" phenomena, there's no reason to think that Obama couldn't buck the trend, but there's a reason the trend exists.