Stormy Daniels' lawyer, Clark Brewster, issued a statement on the indictment, saying: "The indictment of Donald Trump is no cause for joy. The hard work and conscientiousness of the grand jurors must be respected. Now let truth and justice prevail. No one is above the law."

While the indictment remains under seal, Trump had been under investigation by the Manhattan district attorney over a $130,000 payment he made to the adult film actress to keep her from going public with a claim of an affair, which he denies.

Donald Trump being formally accused of a crime could change the outlook for the still-forming field of Republican presidential candidates in 2024 -- either rallying primary voters primed by his talk of the "deep state" and "retribution" or opening up an unprecedented line of criticism for Trump's rivals.

The indictment itself isn't disqualifying, legally speaking. The U.S. Constitution doesn't prevent people under indictment or criminal investigation from running for the White House, experts have told ABC News, so the former president could still be reelected despite the indictment -- and would still be eligible even if it leads to a conviction, regardless of practical obstacles like potential incarceration.

ABC News has learned that former president Donald Trump has been indicted, according to multiple sources with knowledge. The charges were not immediately clear.

Manhattan District Attorney Alvin Bragg has notified Trump.

Trump's former attorney, Michael Cohen, said in a statement, "I do take solace in validating the adage that no one is above the law; not even a former President."

"Today’s indictment is not the end of this chapter; but rather, just the beginning," Cohen said. "Accountability matters and I stand by my testimony and the evidence I have provided to [the district attorney's office]."

The Manhattan grand jury weighing charges against former President Donald Trump will not convene on Wednesday and is expected to meet Thursday on other matters, sources familiar with the situation told ABC News.

The proceeding is conducted in secret and the grand jury could be presented with evidence or vote at any time.

As legal experts speculate on what charges lay inside the sealed indictment ahead of former President Donald Trump's expected surrender on Tuesday afternoon, many predict that prosecutors could try out a new legal theory to justify bringing the charges.

"This could be a novel legal theory," said Kate Shaw, a law professor at Cardozo and ABC News contributor, speculating on what charges the public could see against Trump while stressing it's unknown until the indictment is unsealed.

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-ABC News' Libby Cathey