MILWAUKEE -- President Obama and Mitt Romney entered their final weekend of campaigning on Saturday facing a stubborn landscape of competitive states that right to the end are producing equal shares of hope and fear amid conflicting signals about the outcome.
The president, fighting to avoid being turned out of office four years after a rousing and historic victory, sought to shore up his standing in Midwestern states that had backed him enthusiastically last time. He assumed a defensive posture in Iowa and here in Wisconsin, two states where his advisers had openly scoffed at his rival's chances only months ago.
Mr. Romney, in the closing days of his second quest for the White House, worked to harness the enthusiasm running through the Republican Party to overcome the challenges he confronts in building an Electoral College majority. He fought to secure critical states like Florida and Virginia -- where both sides continue to advertise at saturation levels -- without allowing others to slip away.
But after hundreds of millions of dollars in television commercials, months of campaigning and three widely viewed debates, the race was locked in the same dynamic that has defined it from the start: Mr. Obama, burdened by four years of economic struggle and partisan animosity but still an inspiration to his party, holding the slightest of edges in Ohio and other swing states, and Mr. Romney, bearer of the hopes of conservatives and voters convinced the nation is on the wrong path, fighting to overtake him.
The last defining question was whether Mr. Romney's support had hit a ceiling -- blunted by Mr. Obama's opportunity to show leadership in the deadly aftermath of Hurricane Sandy -- or whether he was on the verge of unseating a president in a dramatic finale.
In the closing hours of the campaign, Mr. Obama raced through four states on Saturday as he tried to build enthusiasm among Democrats by declaring, "I've got a lot of fight left in me." And Mr. Romney sought to tap into disappointment and discontent among voters as he rallied supporters, saying, "I promise change, and I have a record of achieving it."
The confidence expressed by both campaigns belied the tight nature of the contest in at least seven states. In their respective headquarters, advisers made convincing cases for why their candidate had the clearer path to 270 electoral votes, but when pressed they admitted to sleepless nights about a result that was expected to come down to only a sliver of the electorate.
The pursuit of Ohio's 18 electoral votes drew the most attention, with the candidates scheduling multiple stops there before Tuesday, but the rest of the landscape was also highly volatile. Mr. Obama had the edge in Nevada and Mr. Romney in North Carolina, strategists agreed, while Colorado, Florida, Iowa, New Hampshire, Virginia and Wisconsin were far closer.
Here in Wisconsin, Mr. Romney rallied voters on Friday as his running mate, Representative Paul D. Ryan, a native son, fought to rewrite the historical trends of a state that has not voted for a Republican presidential candidate since Ronald Reagan in 1984. Republicans lost the state by only a hairbreadth in 2000 after George W. Bush spent months tirelessly campaigning.
"It's always tantalizingly close for Republicans, and I assume that's where we are at with this one," said James E. Doyle, a former Democratic governor of Wisconsin, who was among the early supporters of Mr. Obama.
The defeat of an attempt to recall Gov. Scott Walker of Wisconsin, a Republican, this year left behind a well-trained contingent of voters that Mr. Romney and his team will try to return to the polls. State laws that allow same-day registration in Wisconsin and in Iowa were seen by advisers to the Obama campaign as an advantage in their efforts to turn out younger voters.
Neil Newhouse, the pollster for the Romney campaign, compared the moment in the race to a football game: "It's a tie game, and there's a loose ball." Joel Benenson, the pollster for the Obama campaign, argued instead that Mr. Obama held the edge and that Mr. Romney was running out of time to overcome him.
The duel between Mr. Obama and Mr. Romney also held implications for the fight for the Senate, where Democrats are increasingly hopeful of retaining control, as well as for races in the House, where Republicans are confident of keeping their majority. A burst of campaigning took place on Saturday, with former President Bill Clinton leading the charge for Democrats and Republican governors and other officials fanning across the country.
The close nature of the presidential race was underscored by the travel schedules, which left the candidates crossing paths, including stops on Saturday afternoon only a few miles apart in Dubuque, Iowa, across the Mississippi River from Wisconsin. Four years ago, Mr. Obama carried Iowa and Wisconsin by wide margins, but he has struggled to lock down his support this year, creating an opening for Republicans.
"He's trying to do everything he can to rekindle what he had four years ago, but it's not there," said Gov. Terry E. Branstad of Iowa, a Republican. "Initially, there were a lot of people who were against Obama and weren't that wild about Romney, but over the last few months that has changed, and now there is really genuine enthusiasm for Romney."
The candidates, as they near the end of their contest, are intimately familiar with the metrics and minutiae of the state-by-state races. In Iowa, for example, Democrats were pointing to 17,000 voter registrations in the past month, which narrowed the Republican advantage to about 1,400 voters, down from about 11,000 a month ago.
The campaign played out on Saturday entirely on the terrain that Mr. Obama won four years ago, when he expanded the battleground to Virginia and North Carolina for the first time in a generation. Republicans portrayed Mr. Romney's late push into Pennsylvania, where he was set to have a campaign rally on Sunday, as a sign of strength.
"You have to look at what they're doing now," said Gov. Tom Corbett of Pennsylvania, a Republican. "They're engaging here. They're spending money here. The race is close, and that's when you try to push it over the line."
Yet Democrats portrayed the move as an act of desperation, arguing that the state has not voted for a Republican presidential candidate since the elder George Bush in 1988. The Democratic Party also has a voter-registration advantage of more than one million people in Pennsylvania.
"This is what I would describe as a Hail Mary," said former Gov. Edward G. Rendell of Pennsylvania, a Democrat. "They have found out that it's not likely they'll carry Ohio, and the only way to do the electoral math is to carry Pennsylvania or a Michigan or even a Minnesota."
An aide to Mr. Romney said the campaign had decided to compete in Pennsylvania only after taking steps to finance advertising campaigns and get-out-the-vote operations fully in other states. The indication was that advisers viewed the state as worth a try, given the deadlocked national poll numbers, but not at the expense of anything else.
In interviews, aides to Mr. Obama said he remained competitive in Florida, a state that both sides had viewed as more favorable to Mr. Romney, who would face a hard road to victory without its 29 electoral votes. Obama officials said they were benefiting from outsize support from non-Cuban Hispanic groups that have traditionally backed him and strong turnout in early voting in Miami-Dade and Broward Counties. Data collected by a firm that tracks political advertisements showed that Mr. Obama was running commercials in every corner of the state -- in Panama City and Orlando, Tallahassee and West Palm Beach.
Mr. Romney's campaign officials said they were confident that he would win Florida. But they were not taking chances and scheduled a visit by Mr. Romney to the state on Monday.
They said they were somewhat less certain about Virginia, agreeing with Mr. Obama's strategists that a jump in polling in the state for Mr. Romney after the first presidential debate had subsided some, though they still predicted a victory there. The Obama campaign has reserved commercial time in the Washington area, Richmond and Roanoke, the monitoring data showed, countering a barrage from Mr. Romney, the National Rifle Association and the "super PAC" Restore Our Future.
Mr. Romney was scheduled to make two stops in Virginia on Monday, including one in the northern suburbs, a region that was pivotal to Mr. Obama's becoming the first Democratic presidential candidate in four decades to win the state. It is part of the Romney campaign's strategy of winning over voters who supported Mr. Obama in 2008.
Mr. Newhouse, the pollster for the Romney campaign, said the campaign had wooed enough Obama supporters nationally to make a decisive difference.
The effort has been punctuated by Mr. Romney's recent emphasis on bipartisanship and moderate policy positions after a primary season in which he called himself "severely conservative." It has also included a run of advertisements telling those swept up in the promise of Mr. Obama's last campaign that he had tried but failed, and that it was time to move on.
"I think we did what we needed to do," Mr. Newhouse said, "but we're going to find out Tuesday."
This article originally appeared in The New York Times.