Donald Trump said at the debate that, if elected president, he would instruct his attorney general to appoint a special prosecutor to investigate Hillary Clinton’s use of a private email server while secretary of state.

“If I win, I am going to instruct my attorney general to get a special prosecutor to look into your situation,” Trump said.

Later, in a testy exchange with Clinton, Trump seemed to imply he knew how that investigation would turn out.

“It’s just awfully good that someone with the temperament of Donald Trump is not in charge of the law in our country,” Clinton said.

“Because you’d be in jail,” Trump replied.

It is theoretically feasible that Trump could re-open the investigation into Clinton, though actually substantiating criminal charges would be near impossible. FBI Director James B. Comey has said repeatedly his investigators found insufficient evidence to warrant bringing criminal charges of mishandling classified information, and, testifying before Congress recently, he rejected the notion the probe could be re-opened.

If President Trump were to order the appointment a prosecutor to investigate a political rival — especially with the outcome predetermined — that would politicize the Justice Department in a way that would make many in law enforcement uneasy. Republicans have criticized the investigation in the Clinton case as political, and they have noted that just before Comey announced his recommendation, Attorney General Loretta Lynch met with Bill Clinton aboard her plane. The two have said they did not talk about any investigations, but the meeting generated significant controversy about the politicization of the Clinton probe.

Trump also claimed Sunday that Clinton, after receiving a subpoena from Congress, deleted 33,000 emails. That is not true. What Trump is likely referring to is that Paul Combetta, an IT staffer with Platte River Networks, deleted a batch of emails in 2015, after a congressional committee investigating the 2012 attack in Benghazi, Libya, had requested they be preserved.

FBI investigators determined, though, that no one had directed Combetta to do that. In fact, top Clinton aide Cheryl Mills had sent him the preservation order from Congress. Combetta told investigators he had been asked to deleted the messages the year before and — having realized he failed to do so — went back and did it on his own after he was required to preserve the records.

Clinton’s team did separately delete 31,830 emails that they have said had nothing to do with her job, though they turned over 30,490 to the State Department.

For her part, Clinton asserted Sunday, as she has in the past, that she would not again use a private email server in public office. She also said she was “very committed to taking classified information seriously.”

On that point, the FBI might quibble. Comey has said she and her staffers were “extremely careless” in their handling of classified information, and even if no reasonable prosecutor would bring a case against them for their conduct, an FBI agent who did the same thing might face professional discipline.