The Republican and Democratic presidential candidates collided sharply Tuesday in the wake of the deadly terrorist attacks in Brussels, with GOP hopeful Ted Cruz calling on law enforcement to “patrol and secure Muslim neighborhoods” and his Democratic rivals sternly rebuking him.

The uproar highlighted the deepening rift between Republicans and Democrats on an issue that was poised to gain a fresh foothold in the campaign: the treatment of Muslim Americans amid concerns about terrorism.

Democratic presidential front-runner Hillary Clinton tweeted that Cruz’s proposal was “beneath us” while Vermont Sen. Bernie Sanders said that singling out a religious group would be “unconstitutional” and “wrong.”

Cruz faced only muted criticism from his own party, with Donald Trump – who has called for a ban on the entry of Muslims into the United States – voicing support for the senator’s plan.

Cruz, Trump and Ohio Gov. John Kasich, also took sharp aim at President Obama, portraying his national security strategy as weak. Kasich called on him to cut short his historic trip to Cuba.

Cruz first presented his idea in a written statement that endorsed aggressive steps against a domestic attack but offered few specifics about how they would be implemented.

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“We need to immediately halt the flow of refugees from countries with a significant al Qaida or ISIS presence,” the statement read. “We need to empower law enforcement to patrol and secure Muslim neighborhoods before they become radicalized.”

Asked later to elaborate, Cruz told reporters in New York City he would effectively revive a now defunct and controversial counterterrorism program there that targeted Muslims.

“You would continue the proactive policing that we saw here in New York,” Cruz said. “You would reinstate the program.”

Asked on CNN whether Cruz’s plan is something he would support, Trump responded: “Yes, I would.”

Kasich, the third Republican in the race, struck a different tone. “We are not at war with Islam,” he told reporters while campaigning in Minnesota. “We are at war with radical Islam.”

Democrats swiftly condemned Cruz’s idea.

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“Muslim Americans: this is your country, too. These kinds of proposals are dangerous, hateful, and beneath us,” Clinton wrote in a Twitter message.

Speaking to reporters in Flagstaff, Ariz., one of three states holding Democratic nominating contests on Tuesday, Sanders stood firmly against Cruz’s plan.

“I strongly disagree,” he said. “It would be unconstitutional. It would be wrong. We are fighting a terrorist organization, a barbaric organization that is killing innocent people. We are not fighting a religion.”

The New York City effort cited by Cruz was a secretive unit of detectives that mapped the Muslim community, spying on businesses and mosques and documenting conversations.

Meanwhile, former Florida governor Jeb Bush said he plans to endorse Ted Cruz for president Wednesday, the latest sign that the Texas senator is eagerly seeking to unite Republican Party leaders behind his campaign in an attempt to stop Trump.