But experts said there’s no legal basis to bar Merchan from presiding.

“If there were some facts showing that the judge had become irrational or infuriated then there might be an argument, but simply having sat in these other cases is not grounds for disqualification,” said Steven Lubert, co-author of “Judicial Conduct and Ethics.”

Still, the appearance of bias — something judges try to avoid — persists, according to two court insiders in New York.

A former assistant district attorney in Manhattan who is now a criminal defense lawyer said he was surprised Merchan would oversee District Attorney Alvin Bragg’s prosecution of Trump for charges related to a 2016 hush money payment.

“I don’t think it’s really a great move on the part of the court system to assign the same judge,” said the former prosecutor, who was granted anonymity because he has cases before Merchan.

“I am just shocked that the chief judge doesn’t preside over a case of this significance. The former president getting indicted calls for the chief judge of the court to handle it,” he said, referring to Ellen Biben, the criminal court’s administrative judge.

Biben is also the former head of the New York State Joint Commission on Public Ethics, a one time New York State inspector general and served as a special deputy attorney general for public integrity.

Trump claimed in the Friday Truth Social posting that Merchan was “hand picked by Bragg & the Prosecutors.”

But the Manhattan district attorney’s office has no role in selecting judges. Instead that responsibility lies solely with the court system. Merchan is expected to be the trial judge for the Trump case because he was the judge overseeing the grand jury that voted to indict the former president Thursday afternoon.

A New York court official, who was granted anonymity to discuss internal processes, said judges are picked to oversee grand juries randomly through an assignment wheel. If the grand jury produces an indictment, the judge who has been overseeing the grand jury then handles the ensuing trial, the official said. It was coincidental that Merchan handled both the Trump Org. trial and the grand jury that examined the hush money matter, this person said.

David Bookstaver, former communications director for the New York State Office of Court Administration, said in an interview that Biben, in consultation with others — including the state court system’s chief judge, Tamiko Amaker — could assign a different judge to the case.

Merchan is indisputably experienced. He was first appointed to the New York County Supreme Court — which is what New York state calls the trial court in Manhattan — in 2006 by former New York City Mayor Michael Bloomberg and moved to the criminal court in 2009. Before becoming a judge, he served for seven years as an assistant attorney general in the New York State Attorney General’s Office and before that as an assistant district attorney in Manhattan.

Several lawyers and other court officials who know Merchan said he’s got the right temperament for the job.

“He is very calm and balanced in his management of his courtroom,” said leading criminal defense lawyer Stacey Richman, who has handled several cases before Merchan.

But a second criminal defense attorney agreed that Merchan’s handling of all of the Trump-related cases makes it look like the fix is in, even if it isn’t.

“It appears to me the judicial system ought to get a little more random,” said the second defense attorney, who was also granted anonymity since he practices before Merchan.

While Trump’s defense team may bring a motion for Merchan to recuse himself, it’s probably a nonstarter.

“It’s entirely up to the judge, who will reject a recusal motion,” said Stephen Gillers, a professor at New York University Law School who specializes in judicial ethics.

“That is not a decision that Trump can appeal now. If there’s a conviction then the defendant, Trump, can argue this motion should have been granted,” Gillers explained.

Gillers said the most important thing is that Merchan has the “confidence of his colleagues and an ability to run the case.”

Frank Rothman, who’s practiced in Manhattan Criminal Court for 37 years, said Merchan enjoys that confidence.

“He’s a very thorough guy, even keeled,” Rothman said. “Treats people with respect, no bullshit kind of guy.”

Erica Orden and Wesley Parnell contributed to this report.