"They've done nothing but harass this guy," said Gregg Hough, chair of the Republican party in Belknap County, New Hampshire, predicting the prosecution will boost Trump support "to the moon" if it fails to deliver a convincing conviction.
In a statement on Thursday, Trump called the indictment "Political Persecution and Election Interference at the highest level in history," without providing evidence.
John Feehery, a Republican strategist, described the Manhattan case as "silly" compared to the other probes hanging over Trump's campaign.
At a campaign rally in Waco, Texas on Saturday, Trump likened the criminal investigations against him to a "Stalinist Russia horror show."
Trump remains the front-runner in the 2024 Republican field, with the support of 44% of Republicans in a March Reuters/Ipsos, ahead of DeSantis' 30% support.