Former Senator Rick Santorum (R-Pa.) on Monday cautioned his fellow Republicans against supporting marriage equality, saying that to do so would be "suicidal" for the party.

In an interview with the Des Moines Register, Santorum said he didn't think the party would undergo a radical shift on the issue, even though public opinion has been steadily changing for years, to the point that polls now show a solid majority of Americans support same-sex marriage. And he compared the recent conversion on gay marriage by two Republican senators — Illinois' Mark Kirk and Ohio's Rob Portman — to Republicans splitting with the party on abortion rights decades ago.

"I'm sure you could go back and read stories, oh, you know, 'The Republican Party's going to change. This is the future.' Obviously that didn't happen," Santorum told the Register. "I think you're going to see the same stories written now, and it's not going to happen. The Republican Party's not going to change on this issue. In my opinion it would be suicidal if it did."

Santorum said that while he thought the party should have an open discussion about gay marriage, Republicans should not change their "foundational principles." 

"Just because some of those things happen to be popular right now doesn't mean the Republican Party should follow suit," he said. 

Santorum joins a chorus of conservatives who've bucked the party's big rebranding effort, which is aimed at adopting a softer tone on social issues and attracting a wider swath of voters in future elections. Shortly after Republican National Committee Chairman Reince Priebus announced the findings of the party's "autopsy" report — which recommended that Republicans convince gay voters that "we care about them, too" — former Arkansas Governor Mike Huckabee warned that evangelicals would splinter off to form their own party should the GOP shift on same-sex marriage. Similarly, Newt Gingrich cautioned that a party-wide embrace of same-sex marriage would lead some conservatives to "flake off." 

In the wake of that pushback, Priebus reaffirmed that the party as a whole still opposed gay marriage, and said he believed some of the more controversial elements of the autopsy report would not be implemented anyway. He also made a point of lauding Huckabee as a "model" for the party on the issue.  

In the interview, Santorum also said he doubted that the increasing support for gay marriage was "a well thought-out position by the American public." The Supreme Court is expected to rule in June on two major marriage equality cases, but Santorum said he hoped the court would buck public opinion and uphold traditional marriage.

"I think you'll see, hopefully, a chastened Supreme Court is not going to make the same mistake in the cases as they did in Roe v. Wade," he said. "I'm hopeful the Supreme Court learned its lesson about trying to predict where the American public is going on issues and trying to find rights in the Constitution that sit with the fancy of the day."