The last day of campaigning by the US presidential candidates took them to different states where neither has enough of an advantage.
They were hoping to convince voters just before they make their way to the polling stations.
These are known as the battleground states, notably Colorado, Florida, Iowa, Nevada, New Hampshire, North Carolina, Ohio, Virginia and Wisconsin.
The Pew Research Center’s election weekend survey said Obama held a 48% to 45% lead over Romney – then it suggested 50% and 47%.
Politico gave the two men 48% and 47%, respectively.
The Gallup Institute pegged them even, at 48%.
Some voters have already cast their ballots, in states with a provision for this, slightly more picking Obama over Romney, according to Pew.
The close margins suggest the outcome could be clinched by which side succeeds in getting voters to the polling stations – their own supporters and the undecided voters they need so badly in toss-up states.
The pro-Romney camp insists its voters are “more committed” than Obama’s.
But apart from individuals’ votes there are the votes allotted to each state based on population.
The popular vote-winner in each state gets its electoral count.
Pundits say Obama needs to secure 69 of these, and Romney 79.
If Obama manages to win in Ohio and Iowa, as he is reported likely to do, that would be enough for him.
The only state scheduled to get a last-day visit from both candidates was Ohio, the most critical of the remaining battlegrounds.
Obama held a clear advantage in the last day of campaigning: 237 guaranteed electoral college votes to Romney’s 191.
A minimum 270 electoral college votes is needed for victory.
Analysts say Romney could beat Obama in the popular vote, but the president could still get re-elected by winning the Electoral College.
It happened with Bush and Gore in 2000, and four other times in history.
That’s the race for the White House, but the balance of power in the Senate and the House of Representatives is also up for grabs on Tuesday.