The US presidential candidates are focusing their efforts on key swing states on the penultimate day of campaigning in the White House race.
In Ohio, Democrat and front-runner Barack Obama urged voters to end "the politics that would divide a nation", BBC reported.
In Pennsylvania, Republican John McCain urged supporters to "knock on doors - with your help we can win".
Analysts say that to win the race, Mr McCain needs to win in Ohio while Mr Obama needs to take Pennsylvania.
Ohio, which narrowly voted Republican in 2004, carries 20 electoral votes under the system used in US presidential elections, making it one of the largest states where polls show the result could still go either way. Pennsylvania boasts 21 electoral votes and voted for the Democrats in 2004.
Despite more gloomy news from the opinion polls on Sunday, Mr McCain 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," Mr McCain added, in the first of two rallies in the state.
The BBC's Matthew Price, in Pennsylvania, says Mr McCain has been focusing on conservative Democrats, and independent-minded voters who live in economically depressed areas of the state.
The Arizona senator has appeared more relaxed and confident in recent days and his campaign believes he is staging something of a comeback.
But most polls suggest he may have left it too late, our correspondent says.
Earlier on Sunday, a CNN/Opinion Research Corporation national survey suggested Mr Obama had a seven-point (53%-46%) lead over Mr McCain in the race for the White House.
A Reuters/C-SPAN/Zogby poll saw Mr Obama increasing his lead by one point, leading Mr McCain by 50% to 44%.