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.