AMES, Iowa (AP) — President Barack Obama is poised to eke out a victory in the race for the 270 electoral votes needed to win re-election, having beaten back Republican Mitt Romney's attempts to convert momentum from the debates into support in all-important Ohio, according to an Associated Press analysis a week before Election Day.

While the Democratic incumbent has the upper hand in the electoral vote hunt, Romney has pulled even, or is slightly ahead, in polling in a few pivotal states, including Florida and Virginia. The Republican challenger also appears to have the advantage in North Carolina, the most conservative of the hotly contested nine states that will determine the winner.

While in a tight race with Obama for the popular vote, Romney continues to have fewer state-by-state paths than Obama to reach 270. Without Ohio's 18 electoral votes, Romney would need last-minute victories in nearly all the remaining up-for-grabs states and manage to pick off key states now leaning Obama's way, such as Iowa or Wisconsin.

To be sure, anything can happen in the coming days to influence the Nov. 6 election.

The AP analysis isn't intended to predict the outcome. Rather, it's meant to provide a snapshot of a race that has been stubbornly close in the small number of competitive states all year. The analysis is based on public polls and internal campaign surveys as well as spending on television advertising, candidate visits, get-out-the-vote organizations and interviews with dozens of Republican and Democratic strategists in Washington and in the most contested states.

The analysis shows that Obama probably would win with at least 271 electoral votes from 21 states, including Ohio, Wisconsin and Iowa, and the District of Columbia. Romney seems on track for 206 from 23 states, including North Carolina. Obama won that state in 2008 and campaigned aggressively there this year. But Obama's team acknowledges it is the most difficult state for him to win, and he's paid less attention to it recently.

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Colorado, Florida, Nevada, New Hampshire and Virginia, with a combined 61 votes at stake, could go either way.

"I'm counting on Iowa! Iowa may be the place that decides who the next president is!" Romney said on one of two visits to the state last week. In Ohio last week, a hoarse Obama reminded a Cleveland audience near the end of a six-state marathon: "I need you, Ohio. America needs you, Ohio."

Romney is banking on what his supporters say is late momentum. Obama is betting that his aggressive effort to register and lock in early voters, mainly Democratic-leaning younger and minority voters, will give him an insurmountable advantage heading into Election Day, when more Republicans typically vote than Democrats.

About 35 percent of voters are expected to cast their ballots before Nov. 6, either in person or by mail. More than 5 million people already have voted. No votes will be counted until Nov 6, but some states report the party affiliation of people who have voted. Democrats have the edge in Iowa, Nevada and North Carolina, according to state figures and data collected by the United States Elections Project at George Mason University. Republicans have the early edge in Colorado.

Obama, who won in 2008 in places where Democrats had not for a generation, continues to have several routes to electoral victory. His easiest: win Ohio, Iowa and Wisconsin, which are leaning his way. He could keep the White House with victories in Ohio, Wisconsin and Nevada. If he loses Ohio, he could prevail by sweeping New Hampshire, Iowa, Wisconsin, Nevada and Colorado.

Romney has fewer options. He must carry Florida and Virginia, where Republicans are feeling good about his standing, as well as wrest control of Ohio, and then also win Nevada, Colorado or New Hampshire. If he loses Ohio, Romney must make up for the state's 18 electoral votes by cutting his way through Obama-leaning territory.

At the top of that target list are Wisconsin, carried by Democrats in six straight presidential elections and where Obama has the edge, and Iowa, a perennial swing-voting state.

Romney's campaign began airing advertisements last week in Minnesota, arguing he was staking a claim in likely Obama territory. But even GOP strategists acknowledged the move was aimed at hitting voters in western Wisconsin and pressuring Obama to follow suit. By Friday, Obama's campaign had done just that, although the president has a healthy lead in both polling and organization in Minnesota.

"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.

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Associated Press writer Julie Pace in Washington contributed to this report.