Obama's biggest advantage: Incumbency

Forget the polls, forget the turnout models -- even forget the issues for a moment.

There is one basic, fundamental reason that President Obama has a good chance at re-election -- the same reason that Mitt Romney faces a basic, fundamental challenge.

Obama is an incumbent.

Since George Washington took the first oath of office in 1789, a total of 31 sitting presidents have participated in national elections -- and 21 have won.

For you baseball fans out there, that's a winning percentage of .677.

For whatever reason -- the ability to divert federal dollars, the opportunity to dictate the news cycle, or the desire of voters not to switch horses in midstream -- being an incumbent has been a big advantage in presidential elections.

Sitting presidents have an even better batting average in the 20th and 21st centuries.

Starting in 1900, the year President William McKinley won re-election over William Jennings Bryan, White House occupants have won 14 of 19 races in which they have run.

That's an average of .737.

In the past eight decades, only four sitting presidents have lost elections: Herbert Hoover (to Franklin Roosevelt in 1932), Gerald Ford (to Jimmy Carter in 1976), Carter himself (to Ronald Reagan in 1980), and George H.W. Bush (to Bill Clinton in 1992).

This analysis includes presidents who ascended upon the deaths or resignation of their predecessors, such as Theodore Roosevelt (1901), Calvin Coolidge (1923), Harry Truman (1945), Lyndon Johnson (1963), and Gerald Ford (1974).

This is not a predictive model; we don't know who is going to win the Obama-Romney race.

Romney can take comfort from the fact that sitting incumbents have lost three times over the past four decades; aides say they are modeling their race on the one in 1980, when a late surge propelled Reagan past Carter.

We're just saying that history has shown, time and time again, that it's very hard to beat an incumbent president.