I was fooling around with the Interactive Electoral College map, trying to come up with realistic outcomes for Nov. 5. One relatively likely scenario I came up with had Obama holding on to every state John Kerry won in 2004, as well as winning Iowa, New Mexico, and Colorodo. If that happened, the result be a tie of 269-269, meaning the election would then go to the House of Representatives, which would presumably vote for Obama.
The last time the House decided an election was 1824, in which John Quincy Adams prevailed in a four-man race by offering opponent Henry Clay, who was also conveniently Speaker of the House, the position of Secretary of State in his cabinet. The candidate who had received the most electoral votes, Andrew Jackson, was embittered by the incident and went off to form the modern Democratic Party.