Gov. Ron DeSantis of Florida escalated his hostilities with former President Donald J. Trump on Friday, arguing that his Republican presidential rival was weak on crime and immigration, and accusing him of ceding vital decision-making throughout the coronavirus pandemic to Dr. Anthony S. Fauci.

In an look with the conservative commentator Ben Shapiro, Mr. DeSantis accused Mr. Trump, the G.O.P. front-runner, of “transferring left” on legal justice and immigration points after successful over the get together’s base in 2015 and 2016.

He pledged that he would repeal what is named the First Step Act, a bipartisan legal justice measure signed into regulation by Mr. Trump in 2018 that expanded early-release applications and modified sentencing legal guidelines, together with obligatory minimal sentences for nonviolent drug offenders.

“He enacted a invoice, principally a jailbreak invoice,” Mr. DeSantis mentioned. “It has allowed harmful folks out of jail who’ve now reoffended and actually, actually harm numerous folks.”

This yr, The New York Instances reported that Mr. DeSantis and his allies noticed the legal justice invoice, which Mr. Trump signed on the urging of his son-in-law Jared Kushner — and immediately regretted — as an space of political weak spot, and that Mr. DeSantis had signaled he would use it within the nomination combat. The invoice is unpopular with elements of Mr. Trump’s hard-core base.

However for Mr. DeSantis, assailing Mr. Trump over the First Step Act is probably difficult. Mr. DeSantis himself voted for the primary model of the invoice when he was in Congress, and Trump allies have sought to focus on that truth.

“So now Swampy Politician Ron DeSanctimonious is claiming he voted for it earlier than he voted towards it,” Steven Cheung, a spokesman for Mr. Trump, mentioned in a press release. “He sounds similar to John Kerry. What a phony! He can’t run away from his disastrous, embarrassing, and low-energy marketing campaign announcement. Rookie errors and unforced errors — that’s who he’s.”

(Mr. DeSantis’s allies be aware that the model of the invoice he voted for seemed considerably totally different, and that the ultimate model handed when he was now not within the Home.)

When Mr. Shapiro requested Mr. DeSantis about Mr. Trump’s latest criticism that crime had risen on his watch in Florida, the previous president’s adopted state, Mr. DeSantis bristled and mentioned Mr. Trump’s insurance policies had undermined regulation and order.

Mr. DeSantis stepped up his assaults on his onetime ally, whom he had averted criticizing instantly for months, lower than 48 hours after he entered the race in a bumpy Twitter occasion.

And as Mr. DeSantis appears to veer to the precise on points like crime, a few of his marketing campaign’s inside technique is coming to mild.

At a fund-raising assembly in Miami on Thursday, donors peppered Mr. DeSantis’s high marketing campaign employees members with questions on his coverage positions and the way they need to be offered to different Republicans, in accordance with a leaked audio recording posted on-line by the web site Florida Politics.

One donor raised a query concerning the rightward shift, to which a marketing campaign official ultimately responded, “We simply obtained to win a major so as to be in a common.”

The donors and officers additionally mentioned how one can speak to Republicans who assist abortion rights. (Mr. DeSantis final month signed a six-week abortion ban in Florida, which accommodates restricted exceptions, whereas Mr. Trump has been hesitant to assist a federal ban.)

A employees member provided one doable reply.

“Abortion is secure, authorized and uncommon in Florida,” he mentioned, parroting a phrase coined by former President Invoice Clinton, a Democrat. “It has not been banned,” he added. “It’s restricted.”

In his interview with Mr. Shapiro on Friday, Mr. DeSantis sought to solid himself as unwavering on unlawful immigration, saying that Mr. Trump had attacked him for opposing amnesty laws whereas in Congress.

He additionally faulted Mr. Trump for his administration’s dealing with of the coronavirus outbreak in 2020, particularly the extent of affect exerted by Dr. Fauci, the longtime high infectious illness skilled and face of the federal authorities’s pandemic response.

Dr. Fauci, who retired in January, has been a frequent goal of Republican assaults over points like distant studying, stay-at-home orders and vaccine mandates.

“He responded by elevating Anthony Fauci and actually turning the reins over to Dr. Fauci, and I feel to horrible penalties for the US,” Mr. DeSantis mentioned. “I used to be the chief on this nation in combating again towards Fauci. We bucked him each step of the best way.”

He mentioned that Dr. Fauci ought to have been fired, however Mr. Trump had honored him.

“I feel the truth that Donald Trump gave Anthony Fauci a presidential commendation on Trump’s final day in workplace, that was a intestine punch to hundreds of thousands of individuals round this nation who had been harmed by Fauci’s lockdowns,” Mr. DeSantis mentioned.

A day earlier, in a publish by Mr. Trump on his Fact Social platform, the previous president slammed Mr. DeSantis over Florida’s response to the pandemic. He mentioned that even former Gov. Andrew M. Cuomo of New York had finished a greater job limiting the lack of lives to the virus than Mr. DeSantis had.

Mr. DeSantis described Mr. Trump’s declare as “very weird,” and mentioned that it recommended he would double down on his actions if there have been one other pandemic.