Workers erected barricades around a Manhattan courthouse on Monday as New York City braced for a possible indictment of Donald Trump over an alleged hush-money payment to a porn star during his 2016 campaign.

The barriers went up in preparation for what would be the first-ever criminal case against a U.S. president, two days after he urged his followers on social media to protest what he said was his looming arrest.

A grand jury was expected to indict Trump late on Monday or on Wednesday, Politico reported, for arranging payments to porn star Stormy Daniels. Trump, who is seeking the Republican nomination for the White House again in 2024, had predicted he would be arrested on Tuesday.

But on Monday, the grand jury still appeared to be collecting evidence before deciding whether charges were warranted.

According to a source familiar with the matter, lawyer Robert Costello was due to appear before the closed-door panel at the request of Trump's lawyers because he might provide information that would challenge earlier testimony by Michael Cohen, Trump's former lawyer.

Cohen himself was headed back to the courthouse, another source said, after the Manhattan District Attorney's office asked that Cohen be available as a rebuttal witness.

The investigation by Manhattan District Attorney Alvin Bragg is one of several legal challenges facing Trump. His office did not immediately respond to a request for comment.

Cohen pleaded guilty in 2018 to federal campaign finance violations tied to his arranging payments to Daniels, whose legal name is Stephanie Clifford, and another woman in exchange for their silence about affairs they claimed with Trump.

Trump has denied that any such affairs took place.

NO SIGN OF UNREST

In his call for protests, Trump raised concerns with law enforcement that supporters might engage in violence similar to the Jan. 6, 2021, attack on the U.S. Capitol.

New York Mayor Eric Adams told reporters police were monitoring social media and keeping an eye out for "inappropriate actions" in the city. The New York Police Department said there were no known credible threats.

If charged, Trump would likely have to travel from his Florida home for fingerprinting and other processing. Law enforcement officials met on Monday to discuss the logistics, several media outlets reported.

Sources have said Bragg's office was presenting evidence to a grand jury about a $130,000 payment made to Daniels in the final weeks of the 2016 campaign.

Trump's fellow Republicans have widely criticized the probe as politically motivated.

Florida Governor Ron DeSantis, Trump's rival for the Republican presidential nomination, said on Monday that Bragg was imposing a "political agenda" that compromised the rule of law, but he also took a veiled swipe at Trump.

"I don't know what goes into paying hush money to a porn star to secure silence over some type of alleged affair," he told reporters.

Republicans in the U.S. House of Representatives launched an investigation of Bragg's office with a letter seeking communications, documents and testimony related to the probe.

Trump was impeached twice by the House during his presidency, once in 2019 over his conduct regarding Ukraine and again in 2021 over the attack on the U.S. Capitol by his supporters. He was acquitted by the Senate both times.

SEVERAL LEGAL CHALLENGES

Bragg won a conviction last December against Trump's business on tax fraud charges.

But legal analysts say the hush-money case may be more difficult. Bragg's office will have to prove that Trump intended to commit a crime, and his lawyers will likely employ a range of counterattacks to try to get the case dismissed, experts say.

Trump meanwhile has to contend with other legal challenges, raising the possibility that he will have to shuttle between campaign stops and courtrooms before the November 2024 election.

Trump's lawyers on Monday asked a Georgia court to quash a special grand jury report detailing its investigation into his alleged efforts to overturn his 2020 statewide election defeat.

The filing in Fulton County Superior Court also seeks to have the county district attorney, Fani Willis, recused from the case, arguing that her media appearances and social media posts demonstrated bias against Trump.

Trump faces two civil trials involving former magazine columnist E. Jean Carroll, who claims that Trump defamed her by denying he raped her. A federal judge on Monday denied a request from both sides to combine the two cases into one.