Washington, Oct 28 (IANS): With the White House race still a dead heat, the Nov 6 night could turn out to be the longest night in American political history with no clear winner emerging on the morrow.

With Republican challenger Mitt Romney slightly ahead nationally in polls, but President Barack Obama maintaining a narrow edge in the electoral votes, poll watchers have raised the possibility of one winning the popular vote and the other still regaining the presidency.

That has happened only four times in America's 51 presidential elections in 1824, 1876, 1888 and as recently as 2000 when George Bush won the White House in what Democrats called a 'stolen' election with just 537 more votes in Florida taking him over the threshold in the electoral college even as Democrat rival Al Gore polled half a million more popular votes.

Yet another intriguing possibility is both Obama and Romney finishing locked in a tie of 269 votes each in the 538 member electoral college chosen in winner-take-all elections in all but two states, Maine and Nebraska.

It hasn't happened before, but a few including CNN and ABC News have both worked out five or six different scenarios in seven swing states - Ohio, Florida, Virginia, Nevada, Colorado, New Hampshire and Iowa -- that could see the rival presidential contenders poised at a tantalising 269 - so near and yet so far. Then the ball goes to the House.

But before that, on polling day - always the Tuesday after the first Monday in a leap year -- people would not be directly voting for Obama or Romney or their running mates, but only be picking up largely unnamed "Electors for Barack Obama and Joseph Biden," or "Electors for George Romney and Paul Ryan."

Each state gets 'electors' equal to the combined total of its Senate - two for each state irrespective of the size - and House members allocated on the basis of its population, as Thomas Neale, a specialist in American national government at Congressional Research Service, explained to the foreign media.

Thus California, America's most populous state, has 55 electoral votes, while a number of states like Alaska, Delaware, Montana, Vermont, Wyoming and the Dakotas have just three votes each. The winner takes all of a state's electoral votes.

But a tie or no tie on polling day, the electors will meet in their state capitals on Dec 17 to choose the nation's next president and vice president.

They are duty bound to vote for the winning presidential candidate irrespective of their own party affiliation, but there have been nine 'faithless' electors since 1900, who have voted against the candidates to whom they were pledged.

Then the Congress meets in a joint session on Jan 6, or Jan 7 this year as Jan 6 happens to be a Sunday, to open the ballot boxes received from the states and count the electoral votes and declare the winning pair that takes office on Jan 20.

But if there is a tie, the president is picked up by the new House of Representatives where each state casts a single vote, while the Vice President is elected in the Senate with each senator casting a single vote.

With the composition of the Congress, where Republicans currently hold a majority in 33 state delegations in the House and Democrats control the Senate, unlikely to undergo a dramatic change in the Nov 6 poll, a tie would throw up a very interesting possibility - Romney in the White House with Biden as his VP.