The administration of Gov. Ron DeSantis of Florida must stop threatening television stations with criminal prosecution for airing a political ad in favor of enshrining abortion rights in the state’s Constitution, a federal judge ordered on Thursday.

Judge Mark E. Walker of the Federal District Court in Tallahassee ruled in a temporary restraining order that the threats by the Florida Department of Health to stations across the state likely amounted to “unconstitutional coercion” and “viewpoint discrimination.”

“The government cannot excuse its indirect censorship of political speech simply by declaring the disfavored speech is ‘false,’” Judge Walker, who has frequently ruled against the administration, wrote in his 17-page order. “To keep it simple for the state of Florida: it’s the First Amendment, stupid.”

The order followed an emergency hearing on Thursday after Floridians Protecting Freedom, the organization behind a campaign for an abortion-rights ballot measure known as Amendment 4, sued on Wednesday.

This month, the state’s health department sent several television stations a cease-and-desist letter urging them to stop airing an ad, titled “Caroline,” that is part of the “Yes on 4” campaign. It features a woman named Caroline Williams discussing how she had been diagnosed with stage four brain cancer when she was 20 weeks pregnant.

“Florida has now banned abortion even in cases like mine,” Ms. Williams says in the ad.

The state called the ad “false.” At least one station stopped airing the ad after receiving the department’s letter, the suit said.

“This critical initial victory is a triumph for every Floridian who believes in democracy and the sanctity of the First Amendment,” Lauren Brenzel, the director of the “Yes on 4” campaign, said in a statement on Thursday. “The court has affirmed what we’ve known all along: The government cannot silence the truth about Florida’s extreme abortion ban.”

Mr. DeSantis has vowed to defeat Amendment 4 and has leveraged the power of the state to oppose the measure, leading to several legal challenges. The courts had declined to intervene in prior cases.

Julia Friedland, Mr. DeSantis’s deputy press secretary, said in a statement that Judge Walker had “issued another order that excites the press.”

“The ads are unequivocally false and put the lives and health of pregnant women at risk,” she said. “Florida’s heartbeat protection law always protects the life of a mother and includes exceptions for victims of rape, incest, and human trafficking.”

The campaign is seeking a preliminary injunction against the state. Judge Walker scheduled a hearing for Oct. 29.

A separate lawsuit, filed by opponents of Amendment 4 and seeking to toss the measure from the ballot, is pending in state court.