When the votes were counted, Maine Sen. Olympia Snowe stood alone, the only Republican to oppose a hotly contested amendment that would have granted employers the right to withhold insurance coverage for any health service they find objectionable for religious or moral reasons. Senate Minority Leader Mitch McConnell runs a tight ship, and that was one of the reasons Snowe announced earlier this week that she is ending her campaign for reelection and leaving the Senate. As one of the few moderates left in the Republican caucus, she had grown tired of the pressure to always toe the line. Snowe’s isolation was stark as the amendment was voted down, 51 to 48: almost all Democrats were on one side and Republicans on the other.

The tight tally “is just another sign of polarization,” says Jack Pitney, a professor of American politics at Claremont McKenna College. “The center is a lonely place and getting lonelier with every election.”

In the lead-up to the vote, Republicans portrayed the “Respect for Rights of Conscience Act” as an effort to keep government out of health-care decisions, while Democrats said it was so broadly written that employers citing moral objections would be empowered to cut off everything from prenatal care for children of single mothers to HIV screening. When Snowe went public with her decision to vote against the measure, the question was whether other GOP moderates would follow in her footsteps. None did, not even Susan Collins, her fellow home-state senator. The two women, who typically vote in lockstep, are known as the “Maine twins.”

Republicans looked to Snowe to provide political cover on thorny social issues, and Democrats knew she could generally be counted on to bring along a handful of additional Republican votes once she was persuaded on an issue. Her support of ending the ban on gays in the military was key and she helped persuade Massachusetts Sen. Scott Brown to vote with Democrats on the issue. He is up for reelection in November and looking for ways to demonstrate independence from his party in a state that votes Democratic in a presidential election year. Brown, though, stuck with his party on the so-called Blunt Amendment, named after its principal sponsor, Sen. Roy Blunt of Missouri.

Brown is betting that there are enough independent Catholic votes in his state that see the issue as one of religious freedom as opposed to an assault on contraceptives. Yet his assertion in an op-ed and in a radio ad that Sen. Ted Kennedy would have supported the Blunt Amendment was belied by Thursday’s vote when liberal Democrats who are Catholics, including John Kerry, voted to table the amendment. Kennedy’s son, former congressman Patrick Kennedy, asked Brown to take down the radio ad; Brown refused. “If I were Elizabeth Warren, I’d have Patrick Kennedy cut an ad to say, ‘I knew Ted Kennedy, Ted Kennedy was my father’ …” says Matt Bennett of Third Way, a centrist Democratic group backing Warren in her bid to defeat Brown in Massachusetts.

A Republican activist who worked on Capitol Hill and who does not want to be quoted says the debate over the availability of contraceptives is “way bigger than a wedge issue” because it goes against settled thought for two generations, and makes the Republican Party look out of touch. “Younger people hear [a debate about contraception] and think those people are Martians. They are unlike me or anybody I know or care about. Republicans risk becoming irrelevant to a whole generation of people, and I include Catholics in that. This is a private matter between a woman, her God, her spouse, and her physician. It’s a crowded enough conversation without government in there.”

Six months ago, Republicans were talking confidently about taking the Senate next November, widening their lead in the House and having a really good chance to win the White House. A debate about social issues that many think has gone off the rails capped by Snowe’s surprise resignation is the latest evidence that their predictions are widely off the mark, particularly in the Senate where Republicans need four seats to gain control. That seemed easy enough with 23 Democrat-held seats being contested, some of them in red states, but Snowe’s departure will likely put Maine into the Democratic column, and Elizabeth Warren, an outspoken consumer advocate, is probably the one Democrat with a chance to defeat Scott Brown in Massachusetts.

That has not escaped the notice of Republicans, who say that if McConnell had let Warren’s nomination go through to head the new Consumer Financial Protection Bureau, the GOP wouldn’t be sweating Brown’s seat. “He can chalk that up to his own stubbornness,” says the GOP activist about McConnell. “He may be running a tight ship, but it’s a small ship, a nice small ship of white guys.” Snowe is one of five Republican women in the Senate, and one of even fewer GOP moderates, which is why she will be missed. “I’m a partisan Democrat, and a pick up is a pick up,” says Third Way’s Bennett. “But you don’t want to lose the only people on the other side who are willing to talk to you. That’s not how we want to pick up seats, and it’s not good for the institution.”