Updated: 4:08 p.m. ET
(CBS News) The Senate on Thursday struck down a controversial amendment that would allow any U.S. employer, not just those affiliated with a religious institution, to deny contraceptive health coverage to its employees based on religious or moral objections.
The so-called "Blunt amendment," sponsored by Republican Senator Roy Blunt, failed in a 51-48 vote. Florida Republican Senator Marco Rubio co-sponsored the measure.
Maine Senator Olympia Snowe was the only Republican to vote against the amendment. Three Democrats -- Pennsylvania's Bob Casey, West Virginia's Bob Manchin, and Nebraska's Ben Nelson -- broke party lines and voted not to table it. Snowe, who recently announced that she will not seek re-election to the Senate, said on MSNBC Wednesday that the amendment was "much broader" than she could support.
The amendment, which was brought up as part of an unrelated transportation bill, was written as a response to a White House mandate that employers must provide women with contraceptive health care. That rule already.
In remarks shortly before the vote, House Speaker John Boehner vowed to continue the fight regardless, telling reporters that "I think it's important for us to win this issue."
"The government, our government, for 220 years has respected the religious views of the American people, and for all of this time there's been an exception for those churches and other groups to protect the religious beliefs that they believe in, and that's being violated here," he said.
Debate over the Obama administration's mandate has given rise to a national controversy over whether or not women should be able to get free access to contraceptive care, either from their own employers or directly from their insurance companies, even if their employers object to morally to birth control.
Republican presidential candidate Mitt Romney was asked about the measure Wednesday and initially said he opposed it. Within hours, however, he said he misunderstood the question andthe amendment.
Both parties have seized on the issue as an important ideological imperative: Republicans argue the Blunt amendment is a necessary protection against the White House mandate, which they argue violates the constitutional right to religious freedom. Democrats, meanwhile, have targeted the measure as the latest effort in what they contend is a continuing assault on women's rights.
In remarks on the Senate floor ahead of Thursday's vote, Senate Minority Leader Mitch McConnell, R-Ky., blasted the White House's contraception rule as violating First Amendment rights.
"Look: this is precisely the kind of thing the founders feared," McConnell said. "It was precisely because of the danger of a government intrusion into religion like this one that they left us the First Amendment in the first place, so that we could always point to it and say, 'No government, no president has that right. Religious institutions are free to decide what they believe. And the government must respect their right to do so.'"
Democratic Senator John Kerry, of Massachusetts, argued the opposite point.
"The Blunt amendment is in fact an assault on" First Amendment objections, he said. "It imposes one view on a bunch of people who don't share that view, or on those who want to choose for themselves."
Democrats say, too, that allowing employers to deny coverage based on moral objections would give employers the right to make far-reaching health care decisions on behalf of their employees.
"Millions of women in this country did not think they would have to wake up this morning and worry about whether or not contraception would be available to them depending on who t heir employer was," said Washington Senator Patty Murray, a Democrat. "It is terrible policy. It will allow any employer in America to cut off any preventive care for any religious or moral reason. It would simply give every boss in America the right to make the health care decisions for their workers and their families."
Murray called the amendment a "radical assault" on preventative health care coverage, and argued that if it passes, employers could cut off coverage to a slew of medical benefits, including prenatal care and immunizations for children.
The issue has taken on national prominence amid the continued heated debate, with political candidates on both sides of the aisle being forced to comment on the politically divisive issue.
Senate Democrats, meanwhile, are seizing on the so-called "culture war" as a key campaign issue in 2012, and recently launched a new ad called "The GOP's War on Women."
In a statement following the vote, Blunt said he was "disappointed" at the "partisanship that has been injected into this debate on religious freedoms."
"Instead of working to pass a bipartisan measure that has been part of our law for almost 40 years, this debate has been burdened by outlandish and divisive efforts to misinform and frighten Americans," he said. "The fact remains that this provision would simply preserve the fundamental religious freedom that we enjoy today. For the first time in our history, the Obama Administration's health care mandate is an egregious violation of our First Amendment rights."
Women's groups, on the other hand, cautiously celebrated the Blunt amendment's defeat, calling it a victory for women's health.
"Today's vote is a win for women," said Nancy Keenan, president of NARAL Pro-Choice America, in a statement. "The senators who voted against birth control will have to answer to their constituents why they would be okay with giving bosses who oppose contraception the ability to deny this coverage to their employees."
Still, NOW President Terry O'Neill warned about similar bills on the horizon.
"NOW is closely watching two similar bills, one authored by Sen. Marco Rubio (R-Fl.) and the other co-authored by Rubio and Sen. Joe Manchin (D-W.Va.). Both bills would allow any employer to strip birth control from their health insurance plans," O'Neill said in a statement. "NOW is urging all reproductive rights supporters to contact their senators to ensure defeat of these bills."
In a press conference following the vote, Senate Majority Leader Harry Reid lauded the Blunt amendment's failure, but lambasted Republicans for loading up the transportation bill with a slew of other amendments.
"Do the Republicans wish for failure?" he asked. "Do they want the economy not to continue to do as well as it is? Because not passing this bill is not going to help the economy."