Trump promises to appoint a special prosecutor

In the last few months of the general election, crowds chanted "lock her up" at every single Donald Trump rally.

And Trump repeatedly told his supporters that he would oblige — promising to ask his attorney general to appoint a special prosecutor to investigate Hillary Clinton and the private email server she used as secretary of state.

"I will ask, to appoint a special prosecutor," he said at an October 2016 rally. "We have to investigate Hillary Clinton, and we have to investigate the investigation."

"She has to go to jail," he said a couple days later.

If he were to carry this promise forward, it would be the first time a president tried to jail his former opponent. However, Trump seems to have backed away from it already.

WHY HE'S PROMISING IT

The FBI already conducted a year-long investigation into Clinton's private email server and whether Clinton or her staff mishandled classified information. Agents concluded that there was not enough evidence to bring criminal charges.

"Although we did not find clear evidence that Secretary Clinton or her colleagues intended to violate laws governing the handling of classified information, there is evidence that they were extremely careless in their handling of very sensitive, highly classified information," said FBI Director James Comey in a July 2016 press conference.

Trump and other Republicans lambasted Comey over the FBI's decision — saying Clinton committed a series of crimes, the investigators made a mistake, and the justice system is trying to protect her.

WHAT NEEDS TO HAPPEN

Trump would have to ask his attorney general to consider appointing a non-government lawyer to serve as a special prosecutor. It is not within a president's authority to order the attorney general to pursue any particular line of inquiry.

Trump nominated Sen. Jeff Sessions, R-Ala., for attorney general. Sessions has been a vocal critic of the FBI's handling of the Clinton email investigation. However, Sessions said during his Senate confirmation hearing Jan. 10 that he would recuse himself if the Clinton email investigation were to move forward.

WHAT'S STANDING IN HIS WAY

There are quite a few signs Trump won't direct his attorney general to seek criminal charges against Clinton.

First of all, it is a norm of American democracy that leaders do not try jail their political opponents. Leading legal experts have said that if the Trump administration were to prosecute Clinton, it would be unprecedented.

"This country doesn't punish its political enemies," Sessions said at his confirmation hearing.

And there's Trump's own feelings on the subject. Despite egging on the "lock her up" chants, he hinted in the weeks following his Nov. 8 win that he would let the whole thing go.

"I don't want to hurt the Clintons, I really don't," Trump told the New York Times in November. "She went through a lot and suffered greatly in many different ways, and I am not looking to hurt them at all. The campaign was vicious."