"We have to keep working those other states, in case Ohio doesn't come through," said veteran GOP presidential strategist Charlie Black, who is advising Romney's campaign.
Ohio is a lynchpin for both candidates.
Obama was in strong standing in the state before the three presidential debates. But Romney's strong performance in the debates helped him gain ground. But Republicans and Democrats alike now say that any momentum Romney had in Ohio from those debates has run its course, and the state gain is leaning toward Obama. New public polls show a tight race.
Operatives in both parties point to the last debate six days ago, and Obama's criticism of Romney's opposition to the automotive industry bailout. They say the criticism was effective in branding Romney as out of touch with working-class voters in a state whose manufacturing economy relies heavily on the car and auto parts industries.
The president started running a new TV ad in the state assailing Romney's position on the aid. Obama's internal polling in Ohio has shown a slight increase in support from white, working-class voters, an important part of Ohio's largely blue-collar electorate.
"That is a killer,'" Tad Devine, a top aide to 2004 and 2000 Democratic nominees, said of the heat Romney is taking for his bailout position. "And it's going to have the biggest impact in the decisive state in the outcome of the election."
Out of necessity, Romney is refusing to cede ground in Ohio, where no Republican has lost and then gone on to win the presidency. He hunkered down in the state for two days last week, and running mate Paul Ryan headlined eight events in the state over the weekend. The impending storm that's set to hit the East Coast led Romney to cancel Virginia campaigning on Sunday and join Ryan in Ohio.
In Ohio alone, Romney and allied groups were spending nearly $9 million on television ads, compared with Obama and his allies' $6 million, and showed no signs of letting up in the final week.
Elsewhere, Obama is looking to stunt any Romney inroad with suburban women, a pivotal constituency, in Colorado and Virginia, by casting the Republican as an extremist on abortion and hammering him on his opposition to federal money for Planned Parenthood.
In Nevada, Romney is banking on the support of fellow Mormons, and noting the high unemployment and foreclosure rates, to overtake Obama. But the president's team is appearing ever more confident of winning the state, partly because of the backing of a booming Hispanic population.
Florida, the biggest battleground prize with 29 electoral votes, is viewed by both sides as a tight. Democrats acknowledge that Romney's standing has improved because of his debate performances and could move out of reach for Obama in the coming days.
Associated Press writer Julie Pace in Washington contributed to this report.
Copyright 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.