Updated

Republican presidential candidate Mitt Romney shifted his focus from the economy to abortion, religious freedom and gay marriage in recent days, part of an intensified effort to win over social conservatives in states voting Tuesday.

It didn't work.

Republican Rick Santorum, a fierce and vocal opponent of abortion and gay rights, trounced the GOP front-runner in Minnesota's caucuses and won bragging rights for placing first in Missouri's non-binding primary. The victories exposed Romney's longtime struggles to convince cultural conservatives that he's now in line with their beliefs despite his previous support of abortion rights. Colorado's conservative GOP electorate also was caucusing.

Before the results were in for that state, Romney told supporters in Denver: "This was a good night for Rick Santorum. I want to congratulate Sen. Santorum, but I expect to become the nominee with your help."

Earlier in the day, the former Massachusetts governor's team had worked to lower expectations in the run up to voting in the three states and the candidate himself had started emphasizing his positions on social issues in the days since he won Saturday's Nevada caucuses. It was a clear sign that he sensed a threat from Santorum, who was challenging Newt Gingrich for the claim of conservative alternative to Romney.

As Romney's day began, he told supporters in Loveland that President Barack Obama was overseeing "an assault on religion — an assault on the conviction and religious beliefs on members of our society."

Romney, who is a Mormon, cited the Obama administration's recent decision to require church-affiliated employers to cover birth control for their employees regardless of the institutions' religious beliefs. Romney called the ruling "a real blow ... to our friends in the Catholic faith" and likened so-called morning-after pills to "abortive pills."

"This kind of assault on religion will end if I'm president of the United States," he said.

Later in the day, Romney pounced after a federal appeals court ruled that a voter-approved ban on gay marriage in California violated the Constitution.

"Today, unelected judges cast aside the will of the people of California who voted to protect traditional marriage," he said in a written statement. "I believe marriage is between a man and a woman and, as president, I will protect traditional marriage and appoint judges who interpret the Constitution as it is written and not according to their own politics and prejudices."

As Romney stepped up his emphasis on social issues, Santorum and rival Gingrich intensified their criticism of Romney on those same issues.

Gingrich, a Catholic, told voters in Ohio that Obama had declared war on the Catholic Church and that Romney was no better than Obama on the issue.

"There's been a lot of talk about the Obama administration's attack on the Catholic Church," Gingrich said at a chili restaurant in Cincinnati. "Well, the fact is, Gov. Romney insisted that Catholic hospitals give out abortion pills, against their religious beliefs, when he was governor."

In late 2005, Romney required all Massachusetts hospitals, including Catholic ones, to provide emergency contraception to rape victims. Some Catholics say the so-called morning-after pill is a form of abortion.

Romney said he did not support the Massachusetts law, which passed despite his veto. But he also said at the time, "My personal view, in my heart of hearts, is that people who are subject to rape should have the option of having emergency contraception or emergency contraception information."

In an op-ed published Tuesday in Politico, Santorum seized on Romney's 2005 decision.

"He said then that he believed 'in his heart of hearts' that receiving these contraceptives — free of charge — trumped employees' religious consciences," said Santorum, a Catholic. "Now, a few years later and running for president, his heart is strategically aligned with religious voters opposing this federal mandate."

Romney's focus came as his campaign prepared for a weak showing Tuesday. Campaign political director Rich Beeson issued a memo to reporters that said Romney won't win every contest. He has lost two of the contests held thus far.

"As our campaign has said from the outset, Mitt Romney is not going to win every contest. John McCain lost 19 states in 2008, and we expect our opponents will notch a few wins, too," Beeson wrote. "But unlike the other candidates, our campaign has the resources and organization to keep winning over the long run."

Santorum, who hadn't won a contest since eking out a victory in Iowa, hoped to ride social conservative support back to relevance. Polling from contests in Florida and Nevada suggest that Romney is still vulnerable among his party's most socially conservative voters.

While Romney scored convincing victories in both states, slightly more evangelical or born-again voters supported Gingrich over Romney in Florida. And while Romney showed improvement among that demographic in Nevada, he won them over by a relatively thin margin.

For now, he's showing no signs of backing off his push for the social conservative vote, even as Republicans and general election voters report that they're far more concerned about the nation's economy.

Romney said the California gay marriage ruling "does not end this fight, and I expect it to go to the Supreme Court."

"That prospect underscores the vital importance of this election and the movement to preserve our values," he said.