Former President Donald J. Trump has claimed that he will be arrested on Tuesday and urged supporters to protest and take back the nation in a social media post. Mr. Trump made the declaration on his site, Truth Social, early on Saturday morning, and while a spokesman later clarified that he had no direct knowledge of the timing of any arrest, the post had an immediate impact. Within hours, Speaker Kevin McCarthy posted on Twitter that he was calling for investigations into whether federal funds were being used for politically motivated prosecutions, a thinly veiled threat to Manhattan’s district attorney. Prosecutors have signaled that an indictment of Mr. Trump could be imminent but have not disclosed when charges would be sought or an arrest made. The charges are expected to stem from a 2016 hush money payment made to a porn star.

While the exact timing of any arrest is still unclear, Mr. Trump’s post has set off a chain of events that could have serious repercussions for the former President and the Republican Party. In the wake of Mr. Trump’s post, supporters have started to organize protests, and there is a growing concern that violence could erupt. The New York officials have been discussing security arrangements at the Manhattan Criminal Court in case of an indictment, according to people with knowledge of the planning.

A message March 18, 2023 on the Truth Social account of former U.S. President Donald Trump reads that he expects to be arrested on Tuesday, March 21 as prosecutors consider charges over hush money payments to a porn star, and calls on his supporters to protest.

Mr. Trump’s declaration has also put Speaker Kevin McCarthy in a difficult position. While he partly owes his position to Mr. Trump, he cannot afford to alienate the Republican base, which still remains largely supportive of the former President. McCarthy’s call for investigations into politically motivated prosecutions is a thinly veiled threat to Manhattan’s district attorney, Alvin L. Bragg. If he follows through with it, he risks further inflaming an already tense situation.

The charges against Mr. Trump are expected to stem from a 2016 hush money payment made to porn star Stormy Daniels, who claimed to have had an affair with Mr. Trump. Mr. Trump’s former fixer and lawyer, Michael D. Cohen, made the $130,000 payment to Ms. Daniels to bury her story of the affair. The payment came in the run-up to the 2016 presidential election, and Mr. Trump subsequently reimbursed Mr. Cohen. Prosecutors are expected to accuse Mr. Trump of overseeing the false recording of the reimbursements in his company’s internal records. The records falsely stated that the payments to Mr. Cohen were for legal services.

Manhattan D.A. says his office will not tolerate threats to the rule of law after Trump calls on supporters to protest

Mr. Trump’s post on Truth Social has set off alarm bells among those who are concerned about the former President’s tendency to use social media to incite violence. The post urging supporters to protest and reclaim the nation carried unmistakable echoes of the incendiary messages he posted online in the weeks before the attack on the U.S. Capitol. In the most notorious of those messages, posted on Dec. 19, 2020, he announced on Twitter that he would hold a rally in Washington on Jan. 6. “Be there,” he told his millions of followers. “Will be wild.”

At that rally, on the Ellipse near the White House, Mr. Trump told supporters to march to the Capitol, where the certification of the 2020 presidential election was taking place. He is under investigation by federal prosecutors for his activities before the attack.

The growing concern about the potential for violence has led to calls for calm from both sides of the political aisle. Speaking on ABC’s “This Week” on Sunday, Representative Alexandria Ocasio-Cortez called for an end to the political rhetoric that she said was inflaming tensions. “I think what’s really important is that we all take a deep breath and understand that we’re all Americans, and that we all have a responsibility to make sure that we’re not inciting violence or encouraging people to do