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.