CENTENNIAL, Colo. – In a marked shift for a candidate who rarely makes overt religious overtures or wades into contentious social issues, Mitt Romney did both here Monday night as he addressed a boisterous rally on the eve of Colorado’s caucuses. 

The Republican presidential front-runner assailed President Obama over a new federal health-care regulation requiring that hospitals, universities and other institutions provide contraceptives and morning-after pills – Romney called them “abortive pills” – to their employees free of charge under their health plans.

 “This is a violation of conscience,” Romney said. “We must have a president who is willing to protect America’s first right: our right to worship God according to the dictates of our own conscience.”

Romney seized a growing controversy in religious and conservative circles at a time when he is trying to beat back a potentially fierce challenge from former senator Rick Santorum, a Catholic whose support among social conservatives is strong. There are signs that Santorum (Pa.) may be surging in some of the states holding non-binding primaries and caucuses on Tuesday. Yet Romney aides rejected the suggestion that he was injecting religious themes into his stump speech because of Santorum, saying their candidate was merely bringing up “issues of the day.”

 The Obama administration policy includes institutions run by churches, leading the Catholic bishops to formally object because it would violate the church’s strict anti-abortion principles.

Romney, a former governor whose views have evolved on a range of social issues, campaigned for office in Massachusetts promising to protect abortion rights but later moved to the right and now is firmly against abortion rights.

 Romney wrote an op-ed, published last week in the Washington Examiner in which he sided with the Catholic bishops and accused Obama of “denying America’s Catholics their constitutionally protected rights.” Romney also tweeted earlier Monday asking supporters to sign a petition “if you’ve had enough of the Obama Administration’s attacks on religious liberty.”

But at a Monday night rally here before about 2,800 people at the Arapahoe High School gymnasium, Romney made his most extensive public comments to date on the subject.

Romney also brought up a recent Supreme Court ruling saying religious institutions are free to choose their ministers, priests and other leaders without any interference from the government.

“I am just distressed as I’ve watched our president try and infringe upon those rights,” Romney said. “The first amendment of the Constitution provides the right to worship in the way of our own choice.

“Do you understand that this administration argued before the Supreme Court that the church should not be able to determine who their ministers are but that government should decide who qualifies as a minister?” Romney added, drawing loud boos from the crowd. “And by the way, you know that some of the members of the court are pretty liberal. You know what they decided? They decided 9-0 that President Obama was wrong.”

Romney expanded his riff to include a broad embrace of the Constitution and the principles of America’s Founding Fathers.

“The king did not give us our rights,” Romney said. “The state did not give us our rights. The creator gave every human being [their rights].”