New York, New York - President-elect Donald Trump's bid to have his conviction in the Stormy Daniels hush money case quashed took a big hit as a New York judge ruled against him.

Judge Juan Merchan said that a Supreme Court decision granting presidents sweeping immunity for official acts did not apply in this case, as testimony at the trial related "entirely to unofficial conduct entitled to no immunity protections."

"Defendant's motion to dismiss the indictment and vacate the jury verdict... is denied."

Monday's ruling raises the prospect that Trump could become the first president to enter the White House with a felony conviction, pending his appeal against the jury's verdict. He was found guilty of paying porn star Daniels for her silence about an alleged sexual encounter, later covering up the payments in an effort to boost his chances in 2016's election.

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Trump has sought to have the case moved to federal court, which would give him the power to end the case himself as soon as he retook the presidency.

He has also challenged the conviction on a number of technical grounds, including alleging juror misconduct.

The judge in the only criminal case against Trump that has gone to trial had indefinitely postponed Trump's sentencing at a hearing on November 22, given his win in the November 5 presidential election.

Trump's legal team had cited a landmark July ruling from the Supreme Court that gives presidents sweeping immunity for official acts committed while in office as justification for their request to throw out this conviction.

Although they opposed Trump's bid to have the case dismissed, prosecutors accepted that the president-elect should receive special treatment to prevent the case interfering with his second White House stint.

"Multiple accommodations well short of dismissal... would satisfy that objective, including a stay of proceedings during his term in office," the prosecutor's office said ahead of Merchan's ruling.

Last month, Trump's lawyers separately asked New York Attorney General Letitia James to quash a civil judgment against him for fraud and a $464 million penalty "for the greater good of the country" as he prepares to return to power.

In a letter to Trump's lawyer John Sauer published on social media, New York Deputy Solicitor General Judith Vale denied the request.