If Barack Obama is defeated, the irresistible comparison will be with Jimmy Carter. A one-term president was rejected after pursuing big government programs amid high energy prices and attacks on America in the Middle East.
Actually, that's not entirely fair to Carter. His budget deficits were minuscule next to Obama's, and in response to the Soviet attack on Afghanistan he began the defense buildup that Ronald Reagan accelerated.
Carter supported airline deregulation, which made air travel widely accessible, as well as rail and trucking deregulation, which squeezed billions from the cost of goods and services. He signed a tax bill cutting capital gains rates and establishing 401(k) deferred-tax retirement accounts.
Obama, in contrast, has made big defense cuts and suggested the sequestration process that threatens cuts his defense secretary calls catastrophic. And in the face of voter disapproval, he pushed through Obamacare and has moved toward more regulation on almost all fronts.
In any case, a Romney victory would look like a refutation of the New Deal historians' narrative -- the idea that Democratic presidents increase the size and scope of government, voters ratify that and Republican successors leave it alone till the next Democrat gets in.
If Obama loses, two of the last three Democratic presidents will have been defeated for re-election. The one who won a second term, Bill Clinton, did so only after he declared, after a Republican off-year victory, that the era of big government was over.
What if Obama wins?
Political analysts almost universally agree that any Obama victory will be by a smaller margin in both popular and electoral votes than his 53 to 46 percent win in 2008. He got a higher share of the popular vote than any other Democratic nominee history except Andrew Jackson, Franklin Roosevelt and Lyndon Johnson.
He's pretty much abandoned two states he won last time, Indiana and North Carolina. In polls after the Oct. 3 debate, he has trailed in Florida.
There has only been one president in American history who won a second term by a smaller popular vote percentage and electoral vote margin than four years before. That was Woodrow Wilson, the Democrat elected in a three-way contest against his two predecessors in 1912 and re-elected in 1916 by 49 to 46 percent in popular votes and 277 to 254 in the Electoral College.
If California, which then had only 13 electoral votes, had not gone for Wilson by 3,773 votes, the incumbent would have lost.