LOVELAND, Colo. — Republican presidential candidate Mitt Romney set aside his focus on the economy in recent days and shifted to abortion, religious freedom and gay marriage, part of an intensified effort to win over social conservatives in GOP caucuses in Colorado and Minnesota on Tuesday.

Romney, who previously supported abortion rights and is now an opponent, has struggled since his 2008 presidential bid to convince some cultural conservatives that he's conservative enough. Rival Rick Santorum, long an outspoken figure on social issues, hopes those voters will help him finish strong on Tuesday.

"Remarkably under this president's administration there is an assault on religion — an assault on the conviction and religious beliefs on members of our society," Romney, a Mormon, told supporters in Loveland during his only campaign event before voters caucus and results are known.

Romney cited the Obama administration's recent decision to require Catholic organizations to provide contraceptive aids in some circumstances. He 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 Newt 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 hasn't won a contest since eking out a victory in Iowa, hopes 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.