Manhattan District Attorney Alvin Bragg's office said in a statement that it has contacted former President Donald Trump's attorney "to coordinate his surrender" for arraignment on a state Supreme Court indictment, noting that it remains under seal.

"Guidance will be provided when the arraignment date is selected," the office said.

In the wake of the indictment, all officers with the New York Police Department have been ordered to show up in uniform Friday morning for deployments around New York City, police sources told ABC News.

There are no credible threats, according to the mayor's office.

The indictment of Donald Trump marks an unprecedented development in the country's history -- the first time a former president has ever faced criminal charges.

Historians say that not since Richard Nixon had there been the real prospect of a commander-in-chief being formally accused of a crime, though Nixon avoided that fate after being pardoned by successor Gerald Ford.

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-ABC News' Tal Axelrod

Republican National Committee Chairwoman Ronna McDaniel called the indictment "a blatant abuse of power from a DA focused on political vengeance."

"When our justice system is weaponized as a political tool, it endangers all of us," she tweeted.

Former Vice President Mike Pence discouraged any protests should a grand jury indict Donald Trump.

"Every American has the right to let their voice be heard. The Constitution provides the right to peaceably assemble. But I think in this instance, I would discourage Americans from engaging in protests if in fact the former president is indicted," Pence said Tuesday when asked by ABC News if Americans should protest a possible indictment.

Pence said he understood the "frustration" while calling the case "politically motivated."

"But I think letting our voices be heard in other ways, and in not engaging in protests, I think is most prudent at this time," he said.

-ABC News' Libby Cathey