After days of new doubts about his campaign, the Florida governor vowed a crackdown on transgender rights in the military and again defended his top rival, Donald Trump.
Gov. Ron DeSantis of Florida, with his poll numbers sagging and his opponents circling, appealed to South Carolina Republicans on Tuesday by doubling down on his attacks over social issues like transgender rights, hoping for a reset for his struggling White House campaign.
But a major shift in tone or strategy from Mr. DeSantis, either toward his main rival, Donald J. Trump, or in the issues he focuses on, did not appear in the offing.
Mr. DeSantis is hoping to quiet his doubters with a rare interview outside the conservative media bubble — he will be on CNN at 4 p.m. Eastern — and a swing through South Carolina, a hotly contested early primary state, where he filed the paperwork formally declaring his presidential candidacy.
The front-runner in the Republican primary, Mr. Trump, has comfortably led polls in the Palmetto State for months, but the twice-indicted former president announced on Tuesday that he potentially faced new federal charges in connection with his efforts to hold onto power after he lost the 2020 election. Even so, Mr. DeSantis defended his rival.
Mr. DeSantis said on Tuesday that Mr. Trump “should have come out more forcefully” on Jan. 6, 2021, to stop the rioting at the Capitol, but he said that any criminal charges would be part of a pattern of weaponization of political institutions against conservatives.
“I think what we’ve seen in this country is an attempt to criminalize politics and to try to criminalize differences,” he said, criticizing what he called the “politicization” of the Justice Department and the F.B.I.
Mr. DeSantis’s social media team, in fact, pushed back on the suggestion that the governor was insufficiently supportive of the former president.
How such deference might undermine Mr. Trump’s lead was unclear. Two other Republican candidates with close ties to South Carolina, Senator Tim Scott and former Gov. Nikki Haley, are also hoping to capitalize on Mr. Trump’s legal peril and Mr. DeSantis’s stumbles and present themselves as the new alternative to the former president.
For Mr. DeSantis, a drastic reboot of his campaign was not obvious.
On Monday night in Tega Cay, S.C., on the North Carolina border, Mr. DeSantis continued to avoid full-on confrontation with Mr. Trump and stuck to his well-worn talking points: the supposed “indoctrination” of children by “leftist” educators; mobilizing the military to the southern border to stop “our country being invaded”; the coddling of “the Chinese Communist Party” by “D.C. elites”; and his disappointment in Mr. Trump for failing to fire Dr. Anthony S. Fauci, who helped lead the Covid-19 response in the final year of the Trump administration.
On Tuesday morning, Mr. DeSantis discussed military policy in an airplane hangar outside Columbia, the capital of South Carolina, a state that is dependent on military bases and has a large veteran population.
His remarks were heavy on themes he has hit since he joined the race: “diversity, equity and inclusion,” which he said he would end in the military, and what he called “woke operating policies” like drag shows, which the Defense Department ended last month. He also talked about transgender issues, proposing to reinstate the Trump administration’s ban on transgender sailors, soldiers and marines, and promising to end transition care for active-duty service members.
“How is that helping ensure a lethal fighting force, to be doing sex-change operations in the military?” he asked.
Mr. DeSantis also said he would reinstate service members who had been relieved of duty for declining to take the Covid-19 vaccine, a move that Defense Secretary Lloyd J. Austin III instituted a year ago.
Although the Trump administration broadly moved against transgender rights throughout the federal government, the DeSantis campaign has framed Mr. Trump as weak on his opposition to rolling back L.G.B.T.Q. rights. It may be having an impact.
Elizabeth James, 69, a retiree and self-proclaimed “grandmama for DeSantis” who lives in the Columbia area, said she supported Mr. Trump in 2016 and 2020 but soured on him after he “waffled” on transgender issues. She applauded Mr. DeSantis’s plans to end military funding for service members’ transition surgeries and said she believed that too few Republican voters knew enough about Mr. Trump’s record on L.G.B.T.Q. issues.
“They’re just holding over from him in 2020 without re-examining where he is now,” she said of the former president. “I think he shifted a lot from where he was.”
Mr. DeSantis has avoided mainstream news outlets, hoping to take his message directly to conservative audiences. But with a news conference on Tuesday morning in West Columbia, S.C., and a taped interview with the CNN host Jake Tapper in the afternoon, the governor is hoping to quiet detractors who say he cannot handle the heat of a critical press.
Newly released fund-raising figures, although strong overall at $20 million, show a candidate spending hand over fist and dangerously dependent on large donors, who could be looking elsewhere for a Trump alternative. Large donors have met in recent days with Mr. Scott and the wealthy entrepreneur Vivek Ramaswamy.
The DeSantis political operation may be strengthening its jabs against Mr. Trump. The DeSantis super PAC Never Back Down confirmed on Tuesday that a new advertisement from the group had used artificial intelligence to mimic the voice of Mr. Trump as if it were attacking Iowa’s popular conservative governor, Kim Reynolds. Politico reported on the ad on Monday evening.
Mr. Trump’s feud with Ms. Reynolds over her refusal to endorse him is real, and began with an attack on his social network, Truth Social. And it could hurt the former president’s chances in Iowa, the state that will cast the first ballots of the primary season in January, given that Ms. Reynolds is exceedingly popular with conservatives.
But the ad falsely purports to catch Mr. Trump on tape. The super PAC said, “Our team utilized technology to give voice to Donald Trump’s words and Truth Social post attacking Gov. Reynolds.”
The open-government group Public Citizen immediately called for the super PAC to take the ad down.
“This ad is racing us down a slippery slope where voters will be unable to distinguish authentic media from fake, A.I.-generated content,” said the group’s president, Robert Weissman.
The Trump campaign evinced no fear.
“The DeSantis campaign doesn’t know how to turn things around with their current candidate,” Jason Miller, a senior adviser for the Trump campaign, said in a statement. He added, “DeSantis could have easily joined one of CNN’s high-profile prime time hosts and reached millions of new voters if he had something compelling to say, but with an unlikable candidate, no campaign message, and rapidly sinking poll numbers, the campaign is doing an afternoon hit that nobody will watch.”
In the meantime, Mr. DeSantis was trying to stake his flag in the South Carolina soil by officially declaring his candidacy. He told the Columbia crowd to expect to see a lot more of him, particularly during the nearly monthlong stretch between the New Hampshire and South Carolina primaries, joking that he and his wife, Casey, might sublease a home in South Carolina.
“I’m excited to be the first Republican candidate to file candidacy paperwork in South Carolina as we continue our mission to reverse American decline by rejecting Bidenomics, stopping the invasion at the border, combating Communist China, and ensuring a better future for our children,” he said in a statement on Tuesday morning. “Help is on the way.”