Obama and Romney in sprint finish

US President Barack Obama and his Republican rival Mitt Romney have launched a frenzied final weekend of campaigning, seeking an edge in a handful of battleground states that will decide the outcome of a tight presidential race which is going down to the wire.

National opinion polls showed a race for the popular vote so close that only a statistically insignificant point or two separated the two rivals.

Ratings in the nine remaining battleground states tightened after Mr Obama's poor performance in the first presidential debate, on October 3, and stayed that way.

Yet Republicans quietly acknowledged that Mr Romney had so far been unable to achieve the breakthroughs needed such pivotal states as Ohio and Wisconsin. That leaves Mr Romney with the tougher path to reach the required 270 electoral votes.

He must win more of the nine most-contested swing states that are not reliably Republican or Democratic: Ohio, Florida, Virginia, North Carolina, Colorado, Nevada, Wisconsin, Iowa and New Hampshire.

After holding mostly small and mid-size rallies for much of the campaign, Mr Obama's team is planning a series of larger events this weekend aimed at drawing big crowds in battleground states. However, the campaign is not expected to draw the massive audiences Mr Obama had in the closing days of the 2008 race, when his rallies drew more than 50,000.

Mr Obama's closing weekend also includes two joint events with former President Bill Clinton: a Saturday night rally in Virginia and an event on Sunday in New Hampshire. The two presidents had planned to campaign together across three states earlier this week, but that trip was called off because of Superstorm Sandy. And, of course, there is always Ohio, the top battleground of them all.

Not to be outdone, Mr Romney hosted a massive rally on Friday night in West Chester, Ohio, drawing more than 10,000 people to the Cincinnati area for an event that featured rock stars, sports celebrities and dozens of Republican officials. It was a high-energy event on a cold night designed to kick off his own sprint to the finish.

The economy has trumped all other issues in a campaign carried out in the shadow of slow growth, high unemployment and huge federal deficits. About 25 million people have already voted in 34 states and the District of Columbia. Mr Obama holds an apparent lead over Mr Romney in key states. But Mr Obama's advantage is not as big as the one he held over John McCain in the 2008 race, giving Mr Romney hope that he could make up that gap in Tuesday's election.

No votes will be counted until Election Day, but several battleground states are releasing the party affiliation of people who have voted early. So far, Democratic voters outnumber Republicans in Florida, Iowa, Nevada, North Carolina and Ohio. Republicans have the edge in Colorado.