Since the start of his presidential campaign, Gov. Ron DeSantis of Florida has pulled his punches during speeches to voters, choosing not to attack the man leading him by 40 points in many national Republican primary polls.
But in recent stump speeches in California, South Carolina, Florida and Iowa, Mr. DeSantis has started attacking former President Donald J. Trump more directly, drawing laughter and applause from his audiences.
Previously, Mr. DeSantis had talked about Mr. Trump, who helped secure his political rise, only when prompted by questions from voters or during interviews with the news media. No longer.
Speaking to a crowd of several hundred people on Saturday at a packed coffee shop north of Des Moines, the Florida governor pointed out that Mr. Trump had gone back on his pledge to make Mexico pay for a border wall, after Mr. Trump suggested recently that it was an impossible promise to keep. Mr. DeSantis tried to draw a strong contrast with his rival, laying out a plan to fund the wall by imposing fees on remittances back to Mexico.
“So I can tell you: Not only will I keep my promises as president, I’ll keep Donald Trump’s promises as president,” the normally staid Mr. DeSantis said with a wry smile as he delivered one of his biggest applause lines of the day. It was a jab he would repeat several times during his three-day bus tour through Iowa over the holiday weekend.
Criticizing a rival might not seem very notable in a presidential campaign. But Mr. Trump is no ordinary rival. He is running in the primary as a popular quasi-incumbent, and his four indictments have only further rallied Republican voters behind him and juiced his fund-raising.
Leading Republicans have tried and failed to figure out how to challenge Mr. Trump since 2015. For an ambitious Republican politician, attacking Mr. Trump without success means angering his loyal supporters who make up a significant portion of the G.O.P. base, potentially forfeiting a future in the Republican Party.
But the response from Mr. DeSantis’s crowds across four states in the last 10 days suggests that there could be a lane for a Republican politician to criticize Mr. Trump without alienating voters — particularly those who support his policies but say they are tired of the drama surrounding him.
Still, going so far as to call Mr. Trump a threat to democracy or characterize his run as an effort to stay out of jail is not likely to play well. Will Hurd, a former congressman from Texas and a long-shot presidential candidate, was booed in Iowa this summer for invoking the indictments against him.
But Mr. DeSantis’s willingness to take on Mr. Trump demonstrates that the race is moving into a new, more pressing phase for his rivals, as Mr. Trump remains miles ahead of the rest of the field in the polls and the first nominating contests are fast approaching. And it could provide a blueprint for other candidates as they look to gain ground and offer themselves as a Trump alternative.
Judy McDonough, 82, said Mr. DeSantis struck the right tone against the former president.
“He didn’t say anything mean or nasty about Trump,” said Ms. McDonough, who voted twice for Mr. Trump. “He stuck to the facts,” she added.
Mr. DeSantis’s more direct strategy began late last month at the second Republican presidential debate. Standing center stage, Mr. DeSantis teed off on Mr. Trump for skipping the debates, taking a far more aggressive tone than he had in the debate a month earlier. Soon after, at a convention of the California Republican Party, Mr. DeSantis criticized the former president for claiming he had turned Florida red, saying he wished Mr. Trump had not “turned Georgia and Arizona blue.”
Now, Mr. DeSantis’s approach to taking on Mr. Trump seems like it will be rooted in addressing a few key policy points from Mr. Trump’s presidency. Among them, based on Mr. DeSantis’s statements so far, will be Mr. Trump’s failures to build the border wall he promised and dismantle what Republicans call the “deep state”; his adding to the national debt; and his handling of the coronavirus pandemic. Mr. DeSantis has also pointed out that Mr. Trump would be able to serve only one term, calling him a “lame duck,” and has gone after his stance on abortion.
Despite Mr. DeSantis raising the pressure on Mr. Trump, their potential showdown is unlikely to combust into fiery theatrics anytime soon. The Florida governor avoids the kind of name-calling and cutting personal attacks that Mr. Trump has used to cow scores of his G.O.P opponents. And besides one or two jabs, Mr. DeSantis’s stump speech remains focused on non-Trump issues, such as inflation, immigration and President Biden’s ability to handle the rigors of the White House.
But there is a sense of heightened urgency for Mr. DeSantis, who has gone all-in on winning the Iowa caucuses, moving a third of his staff to the state last week. With only $5 million on hand for the primary going into the last three months of the year, Mr. DeSantis must make his move on Mr. Trump now or never.
Mr. Trump, of course, has been savaging Mr. DeSantis for months.
On Saturday, as the two men campaigned roughly 100 miles apart in Iowa, Mr. Trump claimed Mr. DeSantis, whom he often refers to by the demeaning nickname “DeSanctimonious,” would soon drop out of the race.
“He’s like a wounded bird going down,” Mr. Trump told a cheering crowd in Cedar Rapids, Iowa.
In typical fashion, Mr. Trump’s spokesman Steven Cheung mocked Mr. DeSantis’s criticisms, saying that his “tough guy routine is laughable.”
“Ron DeSantis has a Little League brain trying to compete in a Major League world,” Mr. Cheung said in a statement. “This is nothing more than a desperate attempt of a flailing candidate who is in the last throes of his campaign.”
As the other candidates battle against Mr. Trump’s overwhelming lead, even the most pro-Trump among them, the entrepreneur Vivek Ramaswamy, has started drawing contrasts with the front-runner, although in Mr. Ramaswamy’s case, quite gently.
“I have something that he doesn’t: I’m from a different generation,” Mr. Ramaswamy, 38, said in response to a question about Mr. Trump, 77, at a SiriusXM town hall in New Hampshire that aired Monday.
Mr. DeSantis debuted his line about the border wall during appearances in South Carolina and Florida this past week, before trotting it out again in Iowa.
Although it generally drew loud applause, the attack did not land with everyone.
Leo Nowak, 69, said he believed Republicans should remain respectful of Mr. Trump even as he acknowledged he was ready to vote for someone else.
“I didn’t like it,” said Mr. Nowak, a retired parole officer who heard Mr. DeSantis speak on Saturday at a hotel in Keosauqua, Iowa. “I don’t like seeing him take shots at Trump, and I don’t like seeing Trump take shots at him.”
But Mr. Nowak said he was ultimately impressed by Mr. DeSantis’s combative conservative message.
“He’s a younger version of Trump,” he said.
And Dennis Moore, 73, a Trump supporter who attended a DeSantis event on Monday at an Iowa ice cream parlor, said he wasn’t worried by the attacks.
Mr. Trump, he noted, “punches back.”
Michael Gold contributed reporting from Cedar Rapids, Iowa and Nick Corasaniti contributed reporting from New York.