BOSTON (AP) – As Massachusetts' epic Senate battle races toward Election Day, voters are facing a stark choice – whether to return a popular Republican incumbent to office or elect the state's first woman to the U.S. Senate, a Democrat making her debut political campaign.

The contest pitting Scott Brown against Elizabeth Warren, a Harvard Law professor, has been one of the hardest fought, most personal, and by far the most costly, political dogfights in Bay State history.

As of mid-October, Brown and Warren had spent a combined $68 million on the race.

Riding on the election is not only one of the state's two U.S. Senate seats, but possibly the balance of power in the Senate, now in the hands of Democrats. Both national parties see the Massachusetts contest as key to their path to political control of the chamber.

Brown has worked throughout the campaign to portray himself as a bipartisan, independent voice who considers each bill on its merits and votes for the best interest of Massachusetts residents, regardless of party.

His closing television ad of the campaign makes no mention of his GOP roots, but instead features an image of Democratic President Barack Obama and concludes with the tag line: “Vote The Person. Not The Party.”

“Things would be a lot better in this country if more people in Washington were willing to think for themselves and work with each other,” Brown says in the ad, adding “I am nobody's senator except yours.”

Warren has worked equally hard to cast herself as a fighter for the middle class, pointing to her work helping create the federal Consumer Financial Protection Bureau. She's also won praise from Obama, who called her “a strong, tireless and determined advocate.”

“Know this, my fight is for you, always has been and I won't back down, no matter how long the odds or how powerful the opposition,” Warren says in her closing ad of the campaign, adding “if you send me to the Senate, I'll work my heart out for you.”

But Warren has also tried to warn of what she said could be the consequences of Brown's re-election. She's said that while Brown has taken “some good votes,” re-electing him could put the Senate into the hands of a far more conservative Republican majority.

Warren says that could have dire consequences for women's health care services, including access to abortion and contraceptives.

While both Warren and Brown describe themselves as “pro-choice,” Warren has faulted Brown for co-sponsoring a measure that would allow employers and insurance companies to refuse coverage for health services, including contraception, on moral grounds.

Brown said he was trying to protect the religious convictions of Roman Catholics, but Warren said a GOP-controlled Senate could go further, even jeopardizing the Supreme Court's Roe v. Wade decision legalizing abortion.

Brown has instead tried to focus on economic issues, portraying Warren as a tax-and-spend liberal in part because of her support of the 2010 federal Affordable Care Act, which he refers to as “Obamacare.” Brown, who has taken a no-new-taxes pledge, said the act would lead to higher taxes for businesses and families in Massachusetts.

Warren has shot back, charging Brown with holding tax cuts for middle class families “hostage” to cuts for “millionaires and billionaires.”

Warren supports the Affordable Care Act, which she said has helped provide insurance for millions of Americans and guaranteed that individuals with preexisting conditions can't be denied coverage.

Brown, who supported the 2006 Massachusetts health law which laid the groundwork for Obama's law, said those kinds of changes are best left to the states instead of the federal government. That echoes a stand taken by former Gov. Mitt Romney, who signed the 2006 health care bill into law.

There have been plenty of sharp elbows in the race.

Brown has criticized Warren's claim of Native American heritage, charging that she used the claim to help secure her post at Harvard Law School, something Warren and those who hired her have denied.

But Warren's inability to provide any documentation of Native American ancestry, and her decision to identify herself as a minority in law school directories from 1986 to 1995, was one of the most serious stumbles of her campaign. Warren said she learned of her family ties to Cherokee and Delaware tribes from stories her parents told her.

In their first debate, Brown chastised Warren saying she “checked the box claiming she is Native American, and clearly she is not.”

The issue later backfired on Brown when some of his staffers were caught on video doing a “tomahawk chop” and shouting war whoops designed to mock Warren as Brown spoke at a campaign rally.

Brown said he condemned the behavior.

The campaign has also been remarkable for the enormous sums raised by both candidates – which have shattered all previous fundraising totals in Massachusetts – and for an unusual pledge signed by Brown and Warren designed to keep outside groups from running television, radio and Internet ads. That deal has largely held.

In the waning hours of the campaign, attention is turning to which party can launch a better “get-out-the-vote” drive.

Republicans say they've put together their largest field organization ever. They say they've contacted more than 2 million voters and will have 35 field offices across the state filled with volunteers.

Warren campaign officials say they're hoping to knock on a million doors and make two million phone calls in the election's final days and are offering seniors and others rides to the polls on Election Day.

Warren is getting a boost from labor unions who are also working to turn out the vote for her.

Whoever prevails on Election Day will have plenty of reasons to crow.

If she wins, Warren will have mounted the first successful campaign for U.S. Senate by a woman in Massachusetts.

If he wins, Brown – who won the 2010 special election to fill the seat left vacant by the death of longtime Democratic Sen. Edward Kennedy – will become the first Massachusetts Republican to win a full six-year Senate term since former Sen. Edward Brooke won reelection in 1972.