A New York judge on Thursday rejected Donald Trump's attempts to dismiss charges of covering up hush money payments to a porn star, setting the stage for the first criminal trial of a former US president to begin on March 25.

At the same time, Trump's representatives attended a fiery hearing in Atlanta, pushing to have the prosecutors bringing separate charges of election fraud and racketeering against Trump disqualified from the case.

They are just two of four criminal cases facing the Republican frontrunner as he campaigns to retake the White House, with his legal teams thus far failing to push the actual trials until after the November 5 vote.

Trump, who has seized on his legal woes to rev up his supporters and denounce Democratic opponent Joe Biden, reiterated his claim that the charges were "just a way of hurting me in the election".

"How can you run for election if you are sitting in a courthouse in Manhattan all day long," he said as he arrived.

In the courtroom, his legal team argued he would not receive a fair trial in New York because another Manhattan jury awarded $83 million to E. Jean Carroll, a writer whom Trump was found to have sexually assaulted and defamed.

Judge Juan Merchan rejected that, as well as arguments by Trump's lawyers that there was too much media coverage for a jury to be unbiased.

"Given all the information I have before me, we are moving ahead to jury selection on March 25," Merchan said.

'Elephant in the room'

Trump, who wore a trademark red tie and dark suit, fidgeted in his seat as his lawyer argued with the judge and prosecutors over jury screening.

"We can't ignore the elephant in the room - Mr Trump is running for president... a juror's political affiliation is something we need to know and understand," said attorney Todd Blanche.

The former president faces 34 counts of accounting fraud linked to payments to porn star Stormy Daniels.

Prosecutors say  Trump illegally covered up remittances to longtime aide Michael Cohen to reimburse him for payments to bury stories about Trump's alleged extramarital sexual relations with Daniels and a Playboy model.

Trump for years encouraged his reputation as a playboy but he denied the affair with Daniels, which she says began in 2006, or just after former first lady Melania gave birth to their son.

A New York grand jury indicted Trump in March 2023 over the payments made to Daniels, whose real name is Stephanie Clifford.

Leaving the courthouse, Trump described the proceedings as a "disgrace."

"It's a rigged state. It's a rigged city. It's a shame," he said.

Legal rollercoaster

Trump's lawyers were also representing him in Atlanta, Georgia, where he is accused of conspiracy to overturn the 2020 election, which he lost to Biden.

That hearing seeks to have District Attorney Fani Willis and her prosecutorial team dismissed from the case over an alleged relationship she had with a top deputy, Nathan Wade.

A combative Willis took the witness stand and emphatically denied that her relationship with Wade began before she hired him to work on the high-profile case.

Willis accused attorneys for Trump and the other co-defendants of spreading lies. 

"It's extremely offensive," she said.

Trump's legal rollercoaster could continue on Friday if, as US media have reported, a ruling is issued in his civil fraud trial, in which he is accused of grossly inflating his property's values.

In that case he risks having to pay up to $370 million and faces a ban from conducting business in New York state.

And he also faces another possible federal trial in Washington, alleging conspiracy to overturn the 2020 election.