In a competition of hawkish messages on Israel, Ron DeSantis pledged on Friday night to revoke the student visas of Hamas sympathizers if elected president, while Tim Scott said he would withhold Pell grants from universities that failed to stamp out antisemitism.

At an Iowa showcase featuring most of the top Republican presidential contenders, the Florida governor and the South Carolina senator engaged in one-upmanship about who would best support Israel, America’s closest Middle East ally.

With their focus on students and academic institutions, they repackaged a traditional line of attack for Republicans: that liberal college campuses foster “woke” extremism, which they said was now taking the form of anti-Israel expressions.

“You see students demonstrating in our country in favor of Hamas,” Mr. DeSantis said. “Remember, some of them are foreigners.”

Mr. DeSantis then warned that if he became president, “I’m canceling your visa and I’m sending you home.”

His remarks, during a tailgate at a construction plant in Iowa City, echoed recent talking points of former President Donald J. Trump, the G.O.P. front-runner, and Senator Marco Rubio of Florida, who sent a letter to Secretary of State Antony J. Blinken this week urging him to rescind the visas of “Hamas sympathizers.”

Mr. Trump, who did not attend the event, had issued a similar pledge to expel student sympathizers of Hamas.

Mr. Scott, who has been polling in the low single digits, said that he had already sponsored a bill — which he would sign if elected president — that would deny Pell grants to colleges and universities that shirk responsibility for condemning support for terrorist groups.

By their inaction, he said, they were sending a message that “it’s OK to be anti-Israel.” He continued, “I say no.”

At a town hall earlier on Friday in Cedar Rapids, Nikki Haley, a former ambassador to the United Nations under Mr. Trump, delivered a similar warning and accused some colleges and universities of promoting violence.

“We have got to start connecting their government funding with how they manage hate,” she said. “Because when you do that, you are threatening someone’s life when you do that. That’s not freedom of speech.”

Ms. Haley, who has been sparring with Mr. DeSantis over the Israel-Hamas conflict as she threatens to eclipse him in some polls, also spoke at the showcase on Friday night. The event was hosted by Representative Mariannette Miller-Meeks, a Republican from a competitive district in Iowa. The state holds its first-in-the-nation presidential caucus in mid-January.

At the event, Ms. Haley called for Israel to wipe out Hamas, a militant group backed by Iran.

“Stop acting like it’s Sept. 10,” she said.

But Vivek Ramaswamy, the biotech entrepreneur, struck a contrast with his G.O.P. rivals, calling for restraint toward an imminent ground invasion by Israel in Gaza. He said that Israel should heed the lessons of the U.S. wars in Afghanistan and Iraq after the Sept. 11, 2001, terrorist attacks.

“To what end?” he said.

Mr. Scott took the opposite view.

”I am sick and tired of people saying to Israel, ‘Settle down,’” he said.

Jazmine Ulloa contributed reporting from Cedar Rapids and Iowa City.