What has never happened before is an incumbent president being returned to office after the majority of the electorate voted to throw him out.

Every modern president to be re-elected — Dwight D. Eisenhower, Richard M. Nixon, Ronald Reagan, Clinton, George W. Bush — has gotten a bigger share of the vote in their second bid for office than their first, and with it, a chance to claim a mandate.

A win in the electoral college that is not accompanied by one in the popular vote casts a shadow over the president and his ability to govern.

If Obama is re-elected that way, “the Republican base will be screaming that Romney should be president, and Obama doesn’t represent the country,” McKinnon predicted. “It’s going to encourage more hyperpartisanship.”