One of the most closely contested presidential elections in U.S. history is coming down to its final hours, with one of the candidates taking the unusual step of campaigning on election day.
Republican nominee Mitt Romney's surprise last-minute decision to schedule Tuesday stops in Cleveland and Pittsburgh follows a frantic Monday in which he and President Barack Obama hopped between swing states, leaning on celebrity friends for an extra boost as they hoarsely implored supporters to double down on their efforts.
But for all the candidates' efforts, which polls suggest have resulted in a virtual tie in national support, the campaign is now mostly out of their hands.
An election that has seen record spending – an estimated $2.6-billion on just the presidential campaigns, and roughly $6-billion when Senate and congressional campaigns are factored in – could come down to a few votes in key battlegrounds such as Ohio, Florida and Virginia.
Despite the heavy public focus on winning over undecided voters, a polarized electorate has made the campaign largely about identifying supporters and getting them out on Tuesday.
So after months of being hyped by both sides, turn-out-the-vote machines will be put to the test.
Mr. Obama is considered to have the more formidable operation on that front, largely because of a sophisticated statistics-based model honed since 2008.
But his campaign also has the biggest challenges.
The President's rise to office four years ago was powered by unusually high turnout among core Democratic constituencies, including minorities and, to a lesser extent, young voters. With Mr. Obama having struggled to meet sky-high expectations for transformational change, some of the enthusiasm is perceived to have waned.
Despite mixed degrees of affection for Mr. Romney personally, Republicans are seen to be highly motivated to defeat Mr. Obama. The catch is that Mr. Romney may have more limited on-the-ground resources, and those could be spread more thinly because their candidate faces a tougher electoral map – needing to carry more of the toss-up states to win the White House.
Alongside the efforts by the parties to get out their votes are allegations that the Republicans are directly or indirectly trying to suppress the Democratic vote. Democrats are pointing to hours-long lineups at advance polls in Florida, where the Republican-dominated state legislature limited the number of early voting days. And they argue that Republican-friendly groups such as True the Vote, ostensibly created to try to crack down on vote fraud, are harassing Democratic voters (particularly from minority groups) to keep them at home.
With disputes over voting rules and their enforcement having already led to a string of legal challenges in recent months, there is an outside chance of the presidential results getting held up in court – a potential repeat of the postelection confusion in 2000, when it took weeks to determine whether George W. Bush or Al Gore had won.
Whether the presidential battle ends Tuesday evening or continues past then, there is a great deal at stake not just for the candidates and their campaign teams, but for supporters who fear having the other side in office at a pivotal moment in their country's history.
Those few votes will determine a number of issues: whether Americans continue with Mr. Obama's relatively interventionist approach to economic recovery or Mr. Romney's more hands-off one; how the looming "fiscal cliff" is navigated; what becomes of health-care expansion in the midst of implementation; and who is charged with trying to promote global stability at a time of turmoil in the Middle East.
Whichever candidate wins, it is unlikely he'll have a clear path to implement his agenda.
Most polls suggest that Democrats will maintain control of the Senate, while Republicans keep the House of Representatives. If so, it will lead to the same sorts of legislative obstacles that Mr. Obama has struggled with since the Democrats lost Congress two years ago.
But at this stage, that's a problem Mr. Obama and Mr. Romney would be glad to have. Now, all they can do is hope that their ground games will give it to them.