On 21 January, Mitt Romney takes the presidential oath of office. Standing close by is his new vice-president, Joe Biden. Highly unlikely though that outcome may be, it's possible under the complex US system for selecting presidents. A 269-269 tie between Romney and Barack Obama in the electoral college, the body set up to formally choose the president, would trigger fall-back mechanisms that might leave the country in a constitutional and political tempest.
Under the constitution's 12th amendment, a tie would bump the choice to the newly elected Congress. The House, which will probably remain in Republican hands, would choose the president, and the Senate, likely to remain controlled by Democrats, would select the vice-president. "If you stipulate that they act according to partisan interests, they would pick Biden, even if the House picked Romney," said Edward Foley, director of the election law programme at Ohio State University's Moritz College of Law in Columbus.
A Romney-Biden administration is perhaps the oddest potential outcome to what could be a complicated finish to the presidential election. The US system is a maze under the best of circumstances. Even as voters express a preference for a candidate when they submit their ballots, they are actually selecting 538 electors, who are allocated in most jurisdictions, though not all, on a state-wide basis.
Those 538 electors then cast ballots in the electoral college, with the top vote-getter becoming president – unless the leader fails to get a majority. In that case, the fall-back mechanisms kick in. The new House would choose the president, voting by state delegations, with a candidate needing 26 states to win. Right now, Republicans control 33 House delegations and Democrats 14, with three states split evenly. The Senate, voting as individuals, would select the vice-president. Counting the two independents who vote with them, Democrats now hold a 53-47 edge in that body.
The constitutional framers set up the system, which the 12th amendment modified in 1804, in anticipation that the House would frequently, perhaps even usually, make the final selection for president. Instead, the fall-back system hasn't kicked in since 1824, when Andrew Jackson was the top vote-getter among four candidates in the electoral college, leading John Quincy Adams, Henry Clay and William Crawford. In the House, Clay threw his support to Adams, securing his election as the country's sixth president. Soon thereafter, Adams named Clay to be his secretary of state, an arrangement Jackson condemned as a "corrupt bargain". Four years later, Jackson won a rematch, ousting Adams.
The potential exists for similar intrigue in 2012. Obama and Romney could reach a 269-269 deadlock in any of several ways. One possibility is that Obama could win Nevada, Virginia, New Hampshire and Colorado, with Romney taking Florida, North Carolina, Ohio, Iowa and Wisconsin. A second scenario would require Romney to win Florida, North Carolina, Iowa, Colorado, Nevada and Virginia, and Obama to capture Ohio, Wisconsin and New Hampshire.
The possibilities would multiply should either Nebraska or Maine produce a mixed result. Both states award some of their electoral votes by congressional district, eschewing the winner-take-all format used in the other 48 states and the District of Columbia. "This is going to be an awfully close outcome, so a 269- 269 tie is certainly possible but very unlikely," said Charlie Cook, editor and publisher of the non-partisan Cook Political Report.
Complicating matters is that the allocation of electors may not be clear for days. A race close enough to produce an electoral college deadlock would probably mean that the results in at least one state would be close enough for the losing side to contest, Foley said. That could involve a delay until provisional and absentee ballots were counted, or it could mean a recount. A candidate who needed to win a recount to achieve a tie might face pressure to concede, particularly if he lost the nationwide popular vote. "The popular vote would really weigh heavily, especially in the context in which one of the candidates hasn't got to 269 and needs to win a recount," said Foley.
And then there are the electors, the little-known figures who will meet in their respective states on 17 December and cast their votes in the electoral college. The vast majority, and perhaps all, will be party loyalists who will vote for the candidate selected by their state's voters. Still, electors sometimes go rogue – as they have nine times over the past 16 elections, according to Robert Alexander, a political science professor at Ohio Northern University.
Even when the vote is a landslide, electors are subjected to heavy lobbying to use their vote to make a statement, said Alexander. More than 80 per cent of electors were lobbied in 2008. "They were lobbied in an election that wasn't close," he said. Should the 2012 vote produce a 269-269 split, the electors would face "an intense lobbying campaign". "Can't you imagine the amount of pressure that would be placed on these human beings to try to resolve the potential Romney-Biden administration before it came to that?"
Only about 30 states bind electors, either through state law or party-enforced pledges. In 2000, Barbara Lett-Simmons, a District of Columbia elector expected to vote for Democrat Al Gore, abstained to protest her city's lack of voting representation in Congress. Even though the nation's capital has no voting representative in Congress, it has three electoral college votes.
Ultimately, it may fall to the nation's political leaders to prevent a Romney-Biden administration. Just as past presidential election disputes have been resolved with an act of statesmanship, Democrats may concede on the vice-presidency if they conclude they can't stop Romney from becoming president. "Some of them might want to go down in history as saying the vice-presidency isn't worth fighting for, for party reasons," Foley said, "and we really ought to do the right thing for the sake of the country."
Expert view: George C Edwards III
How did the electoral college originate? The delegates to the 1787 constitutional convention had a variety of reasons for settling on the electoral college format, but protecting smaller states was not among them. Some delegates feared direct democracy, but that was only one factor in the debate.
Think of how the country looked in 1787. The important division was between states that had slavery and those that didn't, not between large and small states. A direct election for the presidency did not sit well with delegates from the slave states, which had large populations but fewer eligible voters. They saw the electoral college as a compromise because it was based on population. The convention had agreed to count each slave as three-fifths of a person to calculate each state's number of Congress seats. That gave Virginia, which had the largest population among the original 13 states, more clout in choosing the president.
The electoral college distorts the political process by providing a huge incentive to visit competitive states, especially large ones with hefty numbers of electoral votes. That's why Obama and Romney have spent so much time this year in states such as Ohio and Florida. In the 2008 general election, Obama and John McCain personally campaigned in only five of the 29 smallest states.
Supporters argue that the electoral college format prevents candidates from targeting specific groups and regions, instead forcing them to seek votes across the country. But that's not the way it has worked out in recent presidential contests. In 2000, George W Bush lost the popular vote to Al Gore but won in the electoral college. His victory came largely from his support among white men. He did not win majorities among women, blacks, Latinos, urbanites, the young, the old or those with less than average income. In short, Bush claimed the White House with the backing of one dominant group, not with broad support.
The writer is Winant professor of American government at Oxford University