NEW YORK — Paul J. Manafort, President Donald Trump’s former campaign chairman, is now in the sights of Manhattan District Attorney Cyrus R. Vance Jr., whose office is set to bring charges against him. A federal jury in Virginia already convicted Manafort in a financial fraud scheme that could send him to prison for decades, and he has pleaded guilty in Washington to other federal charges.

But Vance’s prosecutors, who are said to be preparing charges to try to ensure that Manafort faces prison even if he is pardoned by the president, likely will face a pitched legal battle and a political firefight.

A federal jury in August convicted Manafort of using foreign accounts to hide millions of dollars from his political consulting work in Ukraine, tax fraud and lying to banks to obtain millions of dollars in loans. State charges, which would be brought by Vance, would be based on some of those same loans, which were issued by Citizens Bank in Rhode Island and Federal Savings Bank in Chicago, according to people with knowledge of the matter.

Manafort’s lawyers are almost certain to challenge any state charges on grounds of double jeopardy, and Vance, a left-leaning district attorney in a blue state, could face the inevitable accusation his prosecution of a member of Trump’s inner circle is politically motivated.

Here is how this may play out.

What is double jeopardy?

Put simply, it is the legal principle that a defendant may not be prosecuted twice for the same crime. This tenet of American jurisprudence is enshrined in the U.S. Constitution. The Fifth Amendment states: No person shall be “subject for the same offense to be twice put in jeopardy of life or limb.”

New York state law provides even stronger protections against double jeopardy. But some exceptions exist. Double jeopardy applies once a jury is sworn in a criminal case, whether the defendant is convicted or acquitted. However, juries sometimes cannot decide on a verdict on a particular charge, which is what happened with several counts in Manafort’s federal case in Virginia. That could leave the door open for Vance’s office to pursue state charges — such as falsifying business records or mortgage fraud — in those instances.

“I don’t imagine when presented with someone whose career is alleged to have been as varied and crooked as Manafort’s, the DA’s office would have to stretch itself to find conduct that could be charged without violating New York’s double jeopardy provisions,” said Daniel C. Richman, a Columbia Law School professor.

Can the president pardon Manafort on state charges?

No. The U.S. Constitution confers broad authority on the president to issue pardons in federal cases. Indeed, the president can even pardon people before they are charged or convicted of a federal crime, although such actions are rare. (President Gerald Ford pardoned his predecessor, Richard M. Nixon, after Watergate, and President Jimmy Carter pardoned Vietnam draft evaders.) But the president has no power to do so in connection with state crimes.

Why people think Trump might pardon Manafort

Trump has repeatedly characterized Manafort as a “brave man,” and indicated that he had not ruled out pardoning his former top campaign official.

“It was never discussed, but I wouldn’t take it off the table,” Trump said in November in an Oval Office interview with The New York Post. “Why would I take it off the table?” the president added.

In the interview, Trump also likened the investigation by the special counsel, Robert Mueller, whose office brought charges against Manafort, to McCarthyism. “This is no better than McCarthy,” the president said, adding, “It’s a terrible thing.”

There will be (political) blood

Beyond the legal battle that would follow any charges against Manafort in New York, there could be political fallout.

Vance taking aim at a member of the president’s inner circle, whether he has been pardoned or not, could play into the narrative that the president and his allies have been subjected to partisan persecution — in the president’s words, a “witch hunt.”

For Vance, the decision to prosecute Manafort would play out before a very different audience. “I assume Vance is motivated in part by political considerations — his constituents expect him to do this,” said Stephen Gillers, a professor at New York University School of Law.

“There’s nothing wrong with that, as long as he’s not doing it only for that reason. He has to also believe it’s the right thing to do,” Gillers said.

The case against Manafort also offers Vance something of an opportunity for redemption. He came under heavy criticism for failing to bring charges against Trump’s eldest children, Ivanka and Donald Jr., after an investigation into allegations they had lied to buyers of units at the Trump SoHo, a 46-story luxury condominium-hotel in Lower Manhattan. Vance defended his handling of the inquiry, saying he ended it largely because the victims would not cooperate with prosecutors after they reached a civil settlement with the Trumps and their business partners.

What happens to Vance’s charges if there is no pardon?

Vance’s office began building the case in order to ensure that Manafort would still be held accountable for his crimes, even if the president pardoned him for his federal convictions. The district attorney’s office is expected to seek charges and prosecute the case against Manafort regardless of whether Trump issues a pardon.

If no pardon is issued and Manafort is convicted on state charges, he almost certainly would serve a state prison sentence at the same time as his federal term. Manafort, 69, has not yet been sentenced on the federal charges.

Paradoxically, one legal expert suggested, Manafort might find himself in a position where a federal pardon portends a far more unpleasant outcome — the prospect of serving time in a New York state institution, where prison life is far more dangerous, dirty and grim.

This article originally appeared in The New York Times.