The US presidential rivals are to spend the final day of campaigning in the race for the White House criss-crossing the country in one last push for votes.
Republican John McCain will speak in seven states from Florida in the east to his own state, Arizona, in the west.
Democrat Barack Obama will travel to Florida, North Carolina and Virginia - all won by the Republicans in 2004.
After one of the costliest campaigns in history, one of the men will on Tuesday be voted the 44th American president.
Both camps are keenly aware of the need to get voters out in the states that polls suggest remain in the balance.
In Ohio on Sunday, Mr Obama told supporters they were "two days from changing America".
Ohio, a narrow Republican win in 2004, has 20 votes under the Electoral College system used in US presidential elections, making it one of the largest "undecided" states.
Under the system, states are apportioned votes based on their population, the biggest being California with 55 votes.
Polls suggest the six closest state races on election day will be in Florida, Indiana, Missouri, North Carolina, Nevada and Ohio.
For his part, Mr McCain urged crowds in Pennsylvania to "knock on doors - with your help we can win". Pennsylvania boasts 21 electoral votes and chose the Democrats in 2004.
Obama offensive, McCain more relaxed
Flush with a record-breaking fundraising operation, Mr Obama has been on the offensive all across the map, but on Sunday focused on Ohio, which has voted for the winning candidate in every presidential election since 1964.
In Cleveland, the Illinois senator told a crowd of 80,000 who had gathered to hear him - and the singer Bruce Springsteen - that he was "feeling good".
"The crowds seem to grow and everybody's got a smile on their face," he said. "You start thinking that maybe we might be able to win an election."
Despite more gloomy news from the opinion polls, Mr McCain has appeared more relaxed in recent days, and his campaign believes he is staging something of a comeback.
In Pennsylvania on Sunday, the Arizona senator told supporters in Wallingford: "We are going to win in Pennsylvania, we are going to win this election - I sense it and I know it. We are going to win here and we are going to bring real change to Washington."
The BBC reports Mr McCain had been focusing on conservative Democrats and independent-minded voters who lived in economically depressed areas of the state. The Vietnam veteran later appeared beside baseball star Curt Schilling at a crowded town hall meeting in Peterborough, New Hampshire.
But the latest CNN/Opinion Research Corporation national survey suggests Mr McCain is trailing by seven points, while a Reuters/C-SPAN/Zogby poll puts Mr Obama ahead by 50% to 44%.
Both campaigns have thousands of volunteers working flat-out manning phone banks, handing out brochures and knocking on doors ahead of the election.
The BBC says millions of Americans - perhaps a quarter of the total turnout - have already voted early, and that now the final rallies are in sight.
An estimated 130 million Americans are expected to cast a vote, in a higher turnout than in any election since 1960.