On Twitter this morning, Sen. John McCain (R-Ariz.) castigated his party’s presidential candidates for embracing waterboarding at this weekend’s CBS News debate.

View Photo Gallery: The leading GOP candidates for president accused President Obama of not being forceful enough to prevent Iran from developing a nuclear weapon.

“Very disappointed by statements at SC GOP debate supporting waterboarding,” the 2008 presidential candidate wrote. “Waterboarding is torture.” (President Obama offered a similar rebuke on Sunday.)

McCain has long been a vocal opponent of torture; he clashed with Romney on the issue in the 2008 campaign. But where do Republican voters stand?

While positions on waterboarding and torture are divided on predictably partisan lines, even Republican opinion on the issue is split.

Rep. Michele Bachmann (R-Minn.), former Godfather’s Pizza CEO Herman Cain , and Texas Gov. Rick Perry all endorsed waterboarding on Saturday, saying it was an effective way of obtaining information from detainees. Former Utah Gov. Jon Huntsman Jr. and Texas Rep. Ron Paul (Texas) disagreed.

Mitt Romney did not weigh in during the debate, but aides later told reporters that the former Massachusetts governor does not believe waterboarding is torture and did not rule out its use in a Romney administration.

At the debate, candidates got cheers for supporting waterboarding — but so did Paul for declaring it torture.

In the 2008 campaign, former Arkansas governor Mike Huckabee agreed with McCain that waterboarding is torture. However, most prominent Republicans have consistently defended so-called “enhanced interrogation techniques.”

Not much polling has been done on the subject since early 2009, when a debate raged over whether the Obama administration should investigate the use of waterboarding under George W. Bush. Polls from that time found that while Americans overwhelmingly believe waterboarding to be torture, they are largely divided on its use.

A 2009 New York Times-CBS News poll found that 71 percent of Americans think waterboarding is a form of torture. When asked if waterboarding could be justified, 46 percent said no, 37 percent said yes, and 7 percent said “depends.”

A CNN poll that same year found 60 percent of respondents believed waterboarding was torture, but approval of the Bush administration’s use of the technique was divided, 50 percent to 46 percent.

In the CNN poll, Democrats were far more likely than Republicans to believe waterboarding to be torture, 75 percent to 44 percent. But that still leaves close to half of Republicans agreeing with McCain.

A January 2009 Washington Post-ABC News poll found that 71 percent of Democrats and 56 percent of independents said torture should never be used, but most Republicans — 55 percent — said the U.S. should consider it in some cases.

So it seems we can say that Republicans generally favor waterboarding, though not in overwhelming numbers. In a campaign dominated by economic issues, foreign policy is not likely to sway many voters one way or the other.

But McCain’s experience as a prisoner of war in Vietnam made it hard for other Republicans to question his stance — and easier for other Republicans to side with him.

No one in the current field has that kind of credibility when it comes to detainee treatment. And as Republicans look to take back the White House in 2012, they might be less tolerant of criticism of Bush.

The candidates are likely afraid to appear weak on national security — except for Huntsman, who aims to differentiate himself from the pack whenever he can, and Paul, who doesn’t care what anyone thinks.

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