The Democratic National Committee sued President Trump on Wednesday over television ads paid for with Homeland Security Department money, calling them illegal propaganda meant to help Republicans in the Nov. 3 midterms.

The complaint, filed in the U.S. District Court for the District of Columbia, names Mr. Trump, the White House, the Department of Homeland Security and the Office of Management and Budget, The Associated Press reported. It says Mr. Trump personally directed the ads. The committee wants a judge to declare them unlawful and stop federal funds from paying for any more. None of the defendants responded right away to the AP’s requests for comment.

“Donald Trump is misusing millions of taxpayer dollars to fund pure propaganda ads in a last-ditch attempt to save Republicans in November — so we’re suing him,” Ken Martin, the committee’s chairman, said in a statement, as Al Jazeera reported.

The 31-page filing explains the timing. “With less than 30 days remaining before the midterm election and millions of public dollars apportioned to pay for propaganda ads still unspent, the DNC has no choice but to take action,” it says, according to Common Dreams. It also argues the spending is beyond the government’s legal authority and violates the Administrative Procedure Act.

The administration set aside $20 million in Homeland Security money for the campaign, drawn from a $175 million package Congress gave the department for Mr. Trump’s immigration enforcement agenda. AdImpact, a media tracking firm, says airing the ads has already cost more than $12 million. NBC News has reported that a Maryland firm won a $20 million contract for the ads.

The spots began running in September. They praise the president and repeat his campaign pitch, and one restated his plan to give every adult U.S. citizen $5,000 if Republicans win next month. Members of both parties have criticized them, and some ran during NFL broadcasts.

On Monday, Mr. Trump called the ads “positive promotion for our Great U.S.A.” and said his super PAC, MAGA Inc., would pay for them from then on. Asked on Tuesday whether he would pay back the money already spent, he said, “we’ll decide.”

That same day, a fifth ad went on the air carrying the line “paid for by the U.S. Government.” It promoted Mr. Trump’s military actions in Venezuela earlier this year.

The DNC says at least $100,000 in public money has gone to the ads since the president’s pledge. Its lawsuit argues that the government is covering the bills so MAGA Inc. can save its own money for Republican candidates.

The White House declined to comment on the suit on Wednesday. It has compared the ads to public service announcements that earlier administrations ran to promote their policies. Federal law bars using money appropriated by Congress for “publicity or propaganda.” Legal scholars quoted by the AP said that, unlike most such announcements, these ads don’t help people use any specific government program.

The suit comes as trust in the vote itself splits along party lines. A Gallup poll released Wednesday found that 37 percent of Republicans and 35 percent of independents have confidence in the country’s elections, compared with 63 percent of Democrats, Al Jazeera reported.

Early voting is already underway in some states. Election Day is Nov. 3.