Former President Donald J. Trump vented about his latest legal defeat to freezing supporters at a Michigan rally on Saturday night, a day after a New York judge fined him nearly $355 million plus interest in his civil fraud case.

The Republican front-runner for his party’s presidential nomination, Mr. Trump denied that he had conspired to manipulate his net worth, which he was found liable of by Justice Arthur F. Engoron in a ruling that could wipe out Mr. Trump’s entire cash stockpile.

“This judge is a lunatic,” he said in his opening salvo at his rally, held inside an airport hangar in Oakland County about 30 miles from Detroit.

Mr. Trump used a similar line of attack against Letitia James, New York’s attorney general, who had accused him of exaggerating his wealth in the lengthy case. Barred by the judge for three years from serving in top roles at any New York company, including portions of his own Trump Organization, Mr. Trump cast aspersions on the justice system and said he had been persecuted.

Mr. Trump’s visit to Michigan overlapped with the first day of early, in-person voting in the state, which is using both a primary and a caucus-style convention to award delegates for the first time in Republican Party contests.

At the rally, the Trump campaign placed large signs urging supporters to take advantage of early voting.

“So you can do that or you can wait a little bit,” Mr. Trump mused to his supporters, many of whom had lined up for several hours in wind chills in the high single digits to low teens to attend.

In his 2016 victory over Hillary Clinton, Michigan played an outsize role for Mr. Trump, who in 2020 lost the state to Joseph R. Biden Jr.

Gretchen Whitmer, Michigan’s Democratic governor and a foil for Mr. Trump, cast the former president on Saturday as a divisive extremist ahead of his visit there.

In a statement issued through the Biden campaign, she said, “Michigan didn’t buy what Donald Trump was selling in 2020, and we won’t in 2024.”

Mr. Trump’s acceptance of early voting was a stark contrast from his contempt toward it in his previous campaigns, when he claimed without basis that it was a recipe for voter fraud.

“If we win Michigan, we’re going to win the election,” Mr. Trump said at his rally. He later continued to spread falsehoods about voter fraud in the state. “We’ve got to watch Detroit. They had more ballots than they had voters.”

The state Republican Party has been consumed in chaos, and this week two rival factions forged ahead with plans to hold dueling conventions on March 2, one in Western Michigan and the other in Detroit.

Both groups have proclaimed fierce loyalty to Mr. Trump, who, like the Republican National Committee, has made it clear whom he wants to lead the party in the key state: Pete Hoekstra, his former ambassador to the Netherlands and a former House member.

“I said, ‘Can you get Hoekstra?’” Mr. Trump said of his endorsement for the role.

But the Trump-styled election denier who has led the Michigan Republican Party for almost a year, Kristina Karamo, is clinging to power. She claims that a Jan. 6 vote to remove her by a group of state party leaders was illegitimate, defying the R.N.C.’s recognition of Mr. Hoekstra on Wednesday as her rightfully elected replacement.

The infighting has drawn unwanted headlines and headaches for Republicans in Michigan, where Mr. Trump was averaging around a 60 percentage point lead over his last remaining rival in the nominating race, Nikki Haley, his former ambassador to the United Nations.

Mr. Trump’s relatively unimpeded march toward the nomination has belied the squall of legal setbacks surrounding him, both in the four criminal cases and other civil cases proceeding against him.

Perhaps the biggest yet came on Friday, with the civil fraud fine, which could exceed $450 million with interest. It also undercut Mr. Trump’s relentlessly curated image of his business empire and personal fortune, his calling card that helped propel him to reality television stardom and then the presidency in 2016.

That judgment, along with recent one by a jury for $83.3 million in a defamation lawsuit brought by the writer E. Jean Carroll, who accused Mr. Trump of a decades-old rape, could deplete the former president’s entire stockpile of cash. (A jury previously found him liable for sexually assaulting Ms. Carroll.)