WASHINGTON - Republican presidential hopeful Rick Santorum said Sunday that he doesn't believe in the separation of church and state, adding that he was sickened by John F. Kennedy's assurances to Baptist ministers 52 years ago that he would not impose his Catholic faith on them.

"I don't believe in an America where the separation of church and state is absolute," Santorum, a devout Catholic, said in an interview from Michigan on ABC's "This Week."

"The First Amendment means the free exercise of religion and that means bringing people and their faith into the public square."

Santorum's latest foray into the hot-button, faith-based issues that so fire up the party's evangelical base comes as his chief rival for the Republican nomination, Mitt Romney, begins to pull ahead slightly in the state of Michigan, where he was born and raised.

Both Michigan and Arizona hold their primaries Tuesday.

While Romney's been battling Santorum in Michigan for the past two weeks, polls suggest he's got a comfortable lead in Arizona, a winner-take-all contest in terms of delegate allocation. Michigan's delegates, on the other hand, are rewarded based on results.

The former Massachusetts governor got a boost Sunday from Arizona Gov. Jan Brewer, who endorsed him as "the man that can carry the day" on NBC's "Meet The Press."

"He has that pro-business background, and he has that political history that I think he would serve America the best."

Brewer's endorsement is considered a boon to Romney's insistence that he's the toughest in the Republican field on illegal immigration. Brewer has been a fierce defender of her state's strict immigration policies, and Romney called Arizona a "model" on the issue in the last Republican debate.

Romney is the native son of Michigan, however, where his father served both as governor and a car company executive. A loss there would be regarded as devastating to his campaign.

Nonetheless, both Romney and Santorum have said they opposed the federal government's bailout of the auto industry in the state where millions work for car manufacturers. Romney even penned a New York Times opinion piece four years ago with the headline: "Let Detroit Go Bankrupt."

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Republican foes have seized upon that headline in advance of a speech by President Barack Obama on Tuesday to the United Auto Workers conference in Washington to celebrate "the rescue of Detroit."

The autoworkers plastered "Let Detroit Go Bankrupt" on 26 American-made vehicles at a Romney event in Detroit on Friday.

Beyond Michigan, however, Santorum's startling stances on social issues like birth control and religion are getting the most attention countrywide.

He's been unapologetic about some of his more controversial remarks, even reiterating Sunday his past remarks that Kennedy's 1960 speech in Houston made "me want to throw up."

"To say that people of faith have no role in the public square? What makes me throw up is someone who is now trying to tell people that you will do what the government says," Santorum said.

"That now we're going to turn around and impose our values from the government on people of faith."

America is all about embracing diversity, he added.

"What we saw in Kennedy's speech was just the opposite, and that's what's so upsetting about it," he said.