Barack Obama has edged ahead of Mitt Romney in the final days of the presidential campaign, helped by his handling of superstorm Sandy, according to a new poll.

As the two candidates criss-crossed the country in a last round of campaigning before Tuesday's election, a survey by the Pew Research Center, one of the more reliable pollsters, showed Obama leading Romney 48% to 45% among likely voters.

Pew estimated that in the final tally, Obama will take 50% of the popular vote to 47% for Romney. The modest lead for Obama marks a shift from a week ago when the two were tied on 47% before Sandy. Among likely voters, 69% said they approved of Obama's handling of the storm.

The findings are similar to a Wall Street Journal/NBC poll published at the weekend. The two offer the first firm evidence of the impact of Sandy on the election. Pew carries one caution for Obama, suggesting turnout may be lower than in 2008 and 2004, which could help Romney.

The poll came as the president's top campaign advisers accused Romney of desperation on Sunday as they claimed the race was moving decisively in Obama's direction. Obama is enjoying a slight edge in polls from most of the crucial swing states that will decide the outcome.

Obama's campaign trail. Photograph: Guardian graphics

Obama and Romney will make eight campaign stops between them on Monday, flying from morning to night across six of the crucial swing states, following similar cross-country dashes over the weekend.

Obama's team claimed that Romney's frantic campaign schedule reflected a sense of desperation, squeezing in a late visit to previously neglected Pennsylvania Sunday in the search for elusive electoral college votes elsewhere. The Obama team also cited visits Monday to Florida and Virginia, two states it said the Romney camp had claimed to have locked up.

In an interview with ABC, David Plouffe, who organised Obama's re-election bid, expressed confidence the president will win on Tuesday, and seized on a comment by Karl Rove that Obama had benefited from superstorm Sandy.

Democrats are interpreting this as Rove, George W Bush's former campaign strategist and co-founder of the Crossroads Super Pac that has poured millions of dollars into Romney's campaign and those of other Republicans, beginning to get his excuses in early.

"A few days ago he [Rove] predicted a big Romney win. My sense is Karl is going be at a crossroads himself on Tuesday when he tries to explain to the people who wrote him hundreds of millions of dollars why they fell up short," Plouffe said.

Obama's campaign trail. Photograph: Guardian graphics

Another Obama strategist, David Axelrod, commenting on Romney's Pennsylvania trip, told Fox News: "They understand that they're in deep trouble. They've tried to expand the map because they know in states like Ohio. They're behind and they're not catching up at this point." He added: "They understand that the traditional, or the battleground, states that we've been focusing are not working out for them."

A Washington Post/ABC poll had the two tied on 48% nationally while a Wall Street Journal/NBC one puts Obama on 48% to Romney on 47%, compared with last week when the two were on 47%.

The WSJ/NBC poll shows Obama is being given credit by likely voters for his handling of hurricane Sandy, with nearly seven in 10 voters approving of his performance, with only 15% disapproving.

Romney's political director Rich Beeson, also on Fox, questioned the credibility of the polls, often a sign of a campaign unhappy with the direction an election is headed, said: "These polls are like nailing Jello to a tree. They are all over the place."

He predicted that independents would turn out in greater numbers for Romney and that Republicans too will flood the polling booths. "There's an intensity factor out there on the side of the Republicans, that is a significant gap and we see it out on the ground, we see it when people are knocking on the doors, we see it when people are making the phone calls," Beeson said.

Asked about a controversial ad that the Romney campaign is broadcasting that claims jeep jobs are being sent to China as a result of Obama's bailout of the motor industry, Beeson ducked the question. Motor manufacturers have denied the claim but the Romney campaign has expanded the number of outlets for broadcasting the discredited ad.

Obama, campaigning alongside Bill Clinton, attracted a crowd of 24,000 for a late-night rally in Virginia on Saturday night and 14,000 in New Hampshire on Sunday. The crowd in Virginia, while respectable for a cold evening, was well down on 2008 when an eve-of-election event at almost the same location attracted more than 80,000.

Although Obama and Romney are tied nationally, Obama appears to be doing better in key swing states. In Iowa, the normally reliable Des Moines Register poll put Obama on 47% to Romney's 42%.

In Ohio, which both campaigns are treating as potentially decisive, attracting more visits than the others, a Columbus Dispatch poll puts Obama on 50% to Romney's 48%.

Campaigning in Iowa yesterday, Romney added a new line to his stump speech, saying that Obama's slogan 'Forward' should be renamed 'Forewarned', that a second term would look much like the first.

Romney too is focused on a remark by Obama on Friday in which he told a crowd in Ohio not to boo. "Voting is the best revenge," Obama said.

Romney, in his speeches, said: "Vote for revenge? Let me tell you: Vote for love of country."

Campaigning alongside Bill Clinton in Concord, New Hampshire, on Sunday Obama drew a parallel with Clinton's presidency.

"Just as we did when Bill Clinton was president, we gotta ask the wealthiest to pay a little bit more so we can reduce the deficit and still invest in the things we need to grow," he said.

Jen Psaki, the president's spokeswoman, said he was energised by the fact that this is the last time he will campaigning on his own behalf. "I think he's really taking in the moments and taking in the times he has backstage with the introducers, and the conversations he has along the rope line, and it is really helping to bolster him through the final days," she told reporters.