(AP Photo/J. Scott Applewhite)

WASHINGTON - Social issues dominated the 2012 presidential race Friday, as President Barack Obama tried to calm a storm over religion and birth control and the Republicans vying to replace him jockeyed to outdo each other in proving their conservative fervour.

Republican front-runner Mitt Romney, who has struggled to win over the party's conservative base during the state-by-state race for the nomination, declared himself "severely conservative" in a speech the Conservative Political Action Conference.

That wasn't enough for former Sen. Rick Santorum, who surprised Republicans by winning this week's caucuses in Colorado and Minnesota. Santorum told the CPAC crowd that even if Romney goes on to defeat Obama this November, it would be a "hollow victory" because Romney isn't conservative enough. Romney has been attacked by his rivals and some conservatives for his shifting stances on social issues since he served a single term as governor of Massachusetts.

Sandwiched between Santorum's and Romney's speeches, Obama announced a much-anticipated change to a rule that would have required religious-affiliated institutions, such as Catholic hospitals, to include birth control in their employee's health insurance plans. Republican presidential candidates and lawmakers and Catholic bishops denounced that as government infringement on religious rights. So Obama on Friday said insurance companies, and not religious institutions, can offer contraceptive coverage to the employees at no cost.

To the White House's relief, major women's rights groups praised the change, and some Catholic groups withheld strong judgment. Democratic strategists said the day's dynamics could result in Republican candidates moving so far to the right that the eventual presidential nominee will struggle to woo crucial independent voters in November.

There was little time left for talk of jobs and the economy, subjects still expected to dominate the November election. In that sense, the day's events may become little more than a footnote.

But Democrats hope the unusually intense focus on social issues, even if temporary, will help them portray Republicans as out of step with average Americans on matters such as access to birth control, equal treatment of men and women, and government philosophies that put problem-solving ahead of ideological purity.

In Washington, Romney skated past details of his time as governor of a Democratic state that trouble some conservatives, including requiring state residents to obtain health insurance. Under Romney's watch, Massachusetts passed a universal health care program that became a model for Obama's historic health care reform.

Santorum, who spoke ahead of Romney without saying his name, said the former governor's health care record would make it impossible for him to draw needed contrasts with Obama. He said Romney had created "the stepchild of Obamacare."

Former House of Representatives Speaker Newt Gingrich, whose campaign has stalled since his big upset win in South Carolina, regaled the CPAC audience with his promises to slash government spending painlessly, through business-tested efficiency techniques.

Like Romney and Santorum, he blasted Obama's contraception policies without delving into details of the latest changes.

"This administration is waging war on religion," said Gingrich, who grew up as a Protestant but converted to Roman Catholicism.

Romney, a Mormon who once supported legalized abortion, vowed to reverse "every single Obama regulation that attacks our religious liberty and threatens innocent life."