WASHINGTON (AP) -- Donald Trump's support for a government database to track Muslims in the United States is drawing sharp rebukes from his Republican president rivals as they try to distance themselves from a proposal that legal expert say is unconstitutional.
Former Florida Gov. Jeb Bush called the prospect of a registry "abhorrent." Florida Sen. Marco Rubio said the idea was "unnecessary" and not something Americans would support. Texas Sen. Ted Cruz, who has largely avoided criticizing Trump throughout the 2016 campaign, said, "I'm not a fan of government registries of American citizens."
"The First Amendment protects religious liberty, and I've spent the past several decades defending the religious liberty of every American," Cruz told reporters in Sioux City, Iowa.
The criticism Friday came after Trump voiced support for a mandatory database for Muslims in the U.S. while campaigning in Iowa the previous day. Trump was asked by an NBC News reporter about the prospect of a database and whether Muslims would be required to be registered. In a video posted by the network, Trump said, "They have to be."
Asked whether Muslims would have to register at mosques, Trump said: "Different places. You sign up at different places. But it's all about management."
In an interview on Fox News Channel on Friday evening, Trump tried to clarify his position. "I want a watch list for the Syrian refugees that (President Barack) Obama's going to let in if we don't stop him as Republicans," he said.
He said he had trouble hearing the NBC reporter's questions. But he did not disavow the idea of a general registry for Muslims living in the country or say decisively he would not support it.
"I want to have watch lists. I want to have surveillance. I mean, we're not a bunch of babies," he said.
Trump has also voiced support for closing certain mosques as a way to contain the terrorist threat in the U.S.
The Islamic State group has claimed responsibility for attacks in Paris that killed 130 people and wounded hundreds more. The attacks have raised fears in the U.S. and prompted calls for new restrictions on refugees fleeing war-torn Syria.
The House passed legislation this past week essentially barring Syrian and Iraqi refugees from the United States. Senate Majority Leader Mitch McConnell, R-Ky., has slotted the bill for possible Senate consideration, though it's unclear whether the chamber could get enough votes to override a threatened veto by President Barack Obama.
The Republican candidates' unified criticism of Trump was striking.
His rivals have vacillated in how they have handled other inflammatory comments from Trump, apparently wary of alienating his supporters while increasingly concerned that he has held his grip on the race deep into the fall.
Civil liberties experts said a database for Muslims would be unconstitutional on several counts. The libertarian Cato Institute's Ilya Shapiro said the idea violates basic privacy and liberty rights.
Marci Hamilton, a Yeshiva University legal expert on religious liberty, said requiring Muslims to register appears to be a clear violation of the Constitution's protection of religious freedom.
"What the First Amendment does and what it should do is drive the government to use neutral criteria," Hamilton said. "You can use neutral criteria to identify terrorists. What it can't do is engage in one-religion bashing. That won't fly in any court."
Democratic front-runner Hillary Rodham Clinton, at a Tennessee rally Friday evening, said, "Mr. Trump has attacked Mexican immigrants, he's attacked women, and now he's attacking Muslim Americans. At some point you have to ask yourself, is that the kind of country we are?"
Vermont Sen. Bernie Sanders said Trump's words were "outrageous and bigoted."
Vice President Joe Biden, who gave the White House's weekly Internet and radio address while Obama was in Asia, said IS wants to "manufacture a clash between civilizations" and to turn away refugees — mostly women, children, orphans, torture survivors — and "say there is no way you can ever get here would play right into the terrorists' hands."
On the GOP side, New Jersey Gov. Chris Christie said creating a national registry based on religion and closing mosques "will do nothing to keep us safer and shows a lack of understanding on how to effectively prevent terrorist attacks."
Ohio Gov. John Kasich said requiring people to register with the federal government because of their religion "strikes against all that we have believed in our nation's history."
Ben Carson, the retired neurosurgeon who has challenged Trump's lead in the GOP race, said the U.S. should have a database on "every foreigner who comes into this country," but he rejected the idea of tracking U.S. citizens based on their religion.
"One of the hallmarks of America is that we treat everybody the same," he said. "If we're just going to pick out a particular group of people based on their religion, based on their race, based on some other thing, that's setting a pretty dangerous precedent."