The race between Romney and Obama remains too close to call less than a week from the Election Day.

Even if Romney wins the popular vote, he will lose the election when Obama beats him in electoral votes.

Meanwhile, both candidates hit the campaign trail hard Thursday.

While U.S. Republican presidential candidate Mitt Romney could win the popular vote in next week's elections, he could still lose the White House if he does not garner enough electoral votes.

In a neck-and-neck race in which the candidates must gain 270 electoral votes to clinch the White House, the race between Romney and President Barack Obama remains too close to call less than a week from the Election Day.

The two candidates were deadlocked in nationwide polls Thursday, while the challenger lagged behind 191 to 201 in electoral votes, according to Real Clear Politics.

Romney took the lead in nationwide polls several times last month, but even if he wins the popular vote, he will lose the election when President Barack Obama beats him in electoral votes.

While each candidate claims a number of states solidly in his corner, 11 are now a toss-up, including Colorado, Florida, Iowa, Michigan, Nevada, New Hampshire, North Carolina, Ohio, Pennsylvania and Wisconsin, according to Real Clear Politics.

John Fortier, director of the Bipartisan Policy Center's Democracy Project, noted the possibility of Romney gaining the popular vote and losing the electoral vote, but added that it was unlikely.

First, states tend to veer toward the direction of the popular vote. Second, while Romney appears to have a slight lead in the popular vote and Obama has a slight lead in several key swing states, it remains unknown how the split will break, if one occurs at all, he said.

"In 2000, the prevailing wisdom was that if there was a split, Gore would win the electoral college and Bush the popular vote," Fortier said, referring to the 2000 election that saw just the opposite occur.

Republican strategist Ford O'Connell said "If I had to bet right now, I'd bet that Romney's going to win Florida, North Carolina and Virginia, and that puts him somewhere around 248 (electoral votes)."

"And the question the Romney camp is really racking their brain over is 'how do we get 22 more electoral votes?'" he said.

For his part, Obama's edge is his campaign's saturation of the air waves in battleground states for the last six months, which could lessen the momentum Romney gained from the Oct. 3 debate when he dominated a lackadaisical Obama, O'Connell said.

The president could also have a leg up in critical Ohio, where one in eight workers is connected to the U.S. auto industry, he added. Obama in 2009 bailed out U.S. auto giants GM and Chrysler.

If the election is decided by the electoral college, it will be the fourth time in history.

In 1876, Republican Rutherford B. Hayes was elected president after losing the popular vote but beat Democrat Samuel J. Tilden by gaining 185 electoral votes -- exactly the number needed to clinch the White House and only one more than his opponent.

In 1888, Republican Benjamin Harrison won the election after losing the popular vote to Democrat Grover Cleveland but winning 233 electoral votes to Cleveland's 168.

And Republican George W. Bush was elected in 2000 after losing the popular vote to then Democratic Vice President Al Gore but winning the electoral vote by 271 electoral votes against Gore's 266.

Meanwhile, both candidates hit the campaign trail hard Thursday after taking a few days off to deal with the effects of Hurricane Sandy, which rocked northeast U.S. and left millions in the dark.

Team Obama is embarking on an intense travel itinerary in the coming days, including stops in key battleground states Wisconsin, Nevada and Colorado. Romney on Thursday campaigned in the critical state of Virginia while running mate Paul Ryan hit events in Nevada and Colorado.

More than 19 million voters have already cast their ballots in states that allow early voting.

While the results will not be reported until the Nov. 6 Election Day, some battleground states have released the party affiliation of voters, showing Democrats with an advantage in Florida, Iowa, Nevada, North Carolina and Ohio and Republicans with an edge in Colorado.