The outcome of Tuesday's U.S. presidential election could closely resemble the 2000 presidential contest, when former President George W. Bush faced off against former Vice President Al Gore and won by a razor's edge.

Back in 2000, Gore won the popular vote, while Bush won the electoral vote and clinched the election.

The current race parallels that dynamic, as Gallup on Monday found challenger Mitt Romney ahead 49 percent to 48 percent nationwide among likely voters while President Barack Obama led in electoral college projections 201 to 191, according to Real Clear Politics.

"On the surface, it appears that Romney has a slight lead in the popular vote and Obama has a slight lead in several key states," John Fortier, director of the democracy project at the Bipartisan Policy Center.

"But it is dangerous to predict how it breaks. 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.

If Romney wins, it will be because of the first presidential debate held in last month, when the former Massachusetts governor came out of his shell and dominated a lackadaisical president.

Indeed, the debate in Denver, Colorado on Oct. 3 was the initial spark that revved up the Romney campaign's engine and allowed him to surge ahead. Prior to that initial contest, Romney was getting pummeled by Democrats' attack ads and seemed unable to come back swinging.

That would also parallel the 2000 elections, in which Bush sealed the deal because his rival appeared testy and inconsiderate during the presidential debates, turning voters off.

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

Some analysts expect Florida, North Carolina and Virginia to go to Romney, which puts the challenger somewhere around 248 electoral votes, leaving it unknown where he will get the 22 remaining votes.

But a Wall Street Journal/NBC News/Marist Poll survey released Friday found that Obama led by a hair in critical Virginia, at 48 percent, while Romney got 47 percent of likely voters.

Still, the game is not over until the ballots are counted, and candidates Monday scrambled to lure undecided voters to their side of the fence, with Romney on Sunday stopping over in Iowa, Pennsylvania, and Virginia. Obama stopped in New Hampshire, Florida, Ohio and Colorado, then stopped Monday in Wisconsin and Iowa.

In such a close race, every last vote makes a difference, and some voters remain undecided just a day before the election. That is not usual: In 2008, 3 percent of the electorate waited until the last three days to decide and 4 percent waited until the last three days to decide in 2004.

In 2000, when the election was razor-close, a whopping 11 percent waited until the last three days to make up their minds, according to exit polls published by the American Enterprise Institute.