Democrat Tim Kaine and Republican George Allen have been deadlocked in Virginia's U.S. Senate race since they both announced a year ago that they were running.

The two former governors are both still popular, both have effective statewide political organizations, both have solid fundraising and, because their race could decide the balance of power in the Senate, both are attracting substantial out-of-state attention and money. Virtually every poll taken since June 2011 shows the race is too close to call.

"We've seen nothing to indicate that this race is going to break early," said Mo Elleithee, a Kaine advisor. "Everything we see shows it's going to be nip and tuck to the end."

One factor that could finally swing the race to either Allen or Kaine is something neither can control: the battle between President Obama and Mitt Romney. Each of the presidential contenders wants -- even needs -- a victory in Virginia on Nov. 6, and both are fighting hard for the state. The number of voters Romney and Obama turn out at the polls could ultimately decide how many votes Kaine and Allen get.

Polling done by Quinnipiac University and provided to The Washington Examiner shows that 85 percent of those voting for Obama also will cast a vote for Kaine. It's the same on the Republican side: Eighty-six percent of Romney's voters plan to vote for Allen.

"You try to unify your base down your ticket. It might be a key strategy, to get everyone in line," said Kyle Kondik, a political analyst at the University of Virginia Center for Politics. "It seems more of a base-turnout election than it is about persuading the small pool of independent and undecided voters."

Still, the poll shows that a significant slice of Virginia voters intend to split their ballots between the presidential and Senate races. Nine percent of Obama's supporters say they'll vote for Allen, while 8 percent of Romney backers intend to vote for Kaine. Given that the numbers are nearly even, and those kinds of crossover voters are unreliable, neither candidate is spending a lot of time courting them.

"I wouldn't hold my breath for Allen-Obama fliers or bumper stickers," said Pete Snyder, who leads the Republican Party's coordinated campaign efforts in Virginia. "I think Gov. Allen is going to stay true to himself and conservative principles."

Allen does have an edge with one key voting bloc, however. Allen has an 8 percentage-point lead over Kaine among independent voters. Allen even leads among independent female voters, whom Kaine has been trying to win over by insisting Allen would curb women's reproductive rights -- a strategy very similar to the one Obama is using against Romney.

Kaine's campaign isn't ceding those independents, however.

"We feel good about where independents are going to break down," Elleithee said. "But there's no question it's going to be close."