McCain-Obama tie possible in US presidential race

"Do you believe for one moment that this won't end up in the courts?" Lichtman said.

Other possible scenarios, according to Bennett:

* Before the House meets, the Obama and McCain campaigns could try to convince the Electoral College voters who actually cast each state's electoral votes to switch their support. This has happened occasionally in past elections but has never affected the outcome of an election. Electors in roughly half of the states are bound by law to honor the popular vote.

* While the House picks a president, the Senate picks the vice president in the event of a tie. The Democratic-controlled chamber could pick Democratic vice presidential candidate Joe Biden even if McCain wins the House vote.

* The newly minted vice president could become acting president if the House doesn't reach a resolution by the time President George W. Bush leaves the White House on Jan. 20.

* House Speaker Nancy Pelosi would become acting president if neither chamber could settle on a president or vice president but she would have to resign her post.

(Editing by David Alexander)