When former President Donald J. Trump was convicted in his New York criminal trial, it took Gov. JB Pritzker of Illinois about 19 minutes to fire off a statement calling him a felon, a racist, a homophobe, and a grifter.
Only one other Democratic governor issued a statement that night about Mr. Trump’s conviction, and the Biden campaign’s response — which came one minute after Mr. Pritzker’s — focused on what Mr. Trump would do as president rather than on the verdict.
Since then, as the Democratic Party and the Biden campaign have wrestled with how to wield the conviction to their advantage, Mr. Pritzker has emerged as the chief amplifier of Mr. Trump’s felon status.
Unlike other top surrogates who have followed Mr. Biden’s lead and kept the focus on Mr. Trump’s policies rather than his conviction, Mr. Pritzker has blazed his own trail of Trump insults — to great cheers from fellow Democrats who are hungry to attack.
“I can’t mince words when it comes to talking about who Donald Trump is,” Mr. Pritzker said in an interview on Wednesday. “It’s important, I think, for people to really refocus on the idea that: Do they really want a president who is a felon who faces jail time?”
Mr. Pritzker’s aggressive approach comes with a warning for his fellow Democrats. In a fiery keynote speech last weekend at the Wisconsin Democratic Party’s convention in Milwaukee, he compared the party to the proverbial frog that does not realize the pot of slowly boiling water it sits in will soon be deadly.
“Donald Trump was convicted of 34 counts by a jury of his peers after being held liable for rape, and the discussion at the water cooler is whether that should be an issue in the presidential race,” Mr. Pritzker said on Saturday. “We’re already in the pot, folks. Republicans have been increasing the temperature for eight years. We better hop out soon or it’s going to boil us all to death.”
As a billionaire blue-state governor who is America’s wealthiest elected official, Mr. Pritzker operates with more freedom to be seen as a slash-and-burn partisan than his colleagues in battleground states.
The biggest applause line in his remarks to Wisconsin Democrats was one that tied together knife-twisting Trump insults with the reality that one of Mr. Biden’s biggest challenges is reminding voters what his rival’s leadership was like.
The former president, Mr. Pritzker said, is an “old man with an orange spray tan who fell asleep at his own trial.” The governor added, “He will count on the American people forgetting how awful his presidency was.”
The Trump campaign did not respond to a request for comment.
Mr. Biden has called Mr. Trump a felon just once publicly in the two weeks since the verdict — during a Connecticut fund-raiser last week that was off-limits to cameras. He had long said he would not discuss Mr. Trump’s legal troubles, sticking to that pledge until the Manhattan conviction.
And when the president’s son Hunter Biden was convicted this week on felony gun charges in federal court, the elder Mr. Biden issued a statement reiterating his love for his son and his respect for the judicial process.
“I will accept the outcome of this case,” Mr. Biden said.
The president’s campaign has issued an array of news releases and fund-raising appeals that used the phrase “convicted felon” to describe Mr. Trump. On Wednesday, the campaign mocked Mr. Trump for not holding public events, sending out a news release with a headline that nodded to his midweek breaks during the six-week trial: “Out of court but still free on Wednesdays.”
“Donald Trump is either too lazy, too tired, or too incapable to campaign after his criminal conviction,” said James Singer, a Biden campaign spokesman.
But Mr. Pritzker has a more confrontational stance, one that is at odds with other Democrats.
The only other Democratic governor to comment on Mr. Trump’s conviction on the day it arrived was Gov. Jared Polis of Colorado, who wrote mildly on social media that “the guilty convictions from a jury of his peers show the former president lacks the moral capacity to lead our country.”
In the interview on Wednesday, Mr. Pritzker said that because voters — particularly those who do not follow the news closely — had so many different sources of information and news, it was incumbent upon Mr. Biden and Democrats to remind them that Mr. Trump is a felon who could face jail time. (He is scheduled to be sentenced on July 11.)
While the Biden campaign has operated under the thinking that voters will reject Mr. Trump because of his policy positions — particularly on abortion rights, health care, and democracy — Mr. Pritzker said the former president’s conviction was what would move voters to back Mr. Biden.
“This is what I believe,” he said. “This is also what I believe is important to most Americans, particularly those in the middle who are ultimately going to decide this election.”
In Wisconsin, Mr. Pritzker’s caustic remarks about Mr. Trump were met with laughter and applause in the ballroom of a Milwaukee casino.
“You had people who will not tire of hearing what a horrible person Trump is,” said Janet Bewley, a former Democratic leader of the Wisconsin State Senate who was elected to be a Biden delegate at the party’s national convention in August. “They love to hear people foaming and they love to foam.”
After speeches from mild-mannered local politicians including Gov. Tony Evers and Senator Tammy Baldwin, Mr. Pritzker’s remarks served as a road test for the sort of red-meat speech that would be at home during the Democratic convention in Chicago. (Speakers at the event have not been announced, but Mr. Pritzker, as the de facto host, is likely to have a slot.)
“It was clear in the room as he was doing it that he was getting more aggressive about the felony conviction,” said Lt. Gov. Sara Rodriguez of Wisconsin. “That is something that’s going to resonate with Wisconsinites. It is going to resonate with independent voters. Do we want a felon in the White House? Is that what we want to do?”