Evidently, as Esper noted, a President may legally invoke the Insurrection Act, which usually has been upon recommendation of the Attorney General, who on January 21, 2025, probably would be an acting attorney general.
A few days earlier, on November 6, The Washington Post had explained
In public, Trump has vowed to appoint a special prosecutor to “go after” President Biden and his family. The former president has frequently made corruption accusations against them that are not supported by available evidence.
To facilitate Trump’s ability to direct Justice Department actions, his associates have been drafting plans to dispense with 50 years of policy and practice intended to shield criminal prosecutions from political considerations. Critics have called such ideas dangerous and unconstitutional....
Much of the planning for a second term has been unofficially
outsourced to a partnership of right-wing think tanks in Washington. Dubbed
“Project 2025,” the group is developing a plan, to include draft executive
orders, that would deploy the military domestically under the Insurrection Act,
according to a person involved in those conversations and internal
communications reviewed by The Washington Post. The law, last updated in 1871,
authorizes the president to deploy the military for domestic law enforcement.
The proposal was identified in internal discussions as an immediate priority, the communications showed. In the final year of his presidency, some of Trump’s supporters urged him to invoke the Insurrection Act to put down unrest after the murder of George Floyd in the summer of 2020, but he never did it. Trump has publicly expressed regret about not deploying more federal force and said he would not hesitate to do so in the future.
As if to validate the Post's reporting, in December the once and possibly future President told Sean Hannity that he would not be a dictator- "except for day one."
Trump claimed that he was referring to expanding oil drilling and closing the southern border with Mexico, which may be two of his policy objectives. However, on January 20 or January 21, he likely would sign an order invoking the Insurrection Act to employ the military domestically, shutting down dissent and facilitating persecution and prosecution of his political enemies.
In response to Trump's promise, Biden campaign manager Julie Chavez Rodriguez issued a statement noting "Donald Trump has been telling us exactly what he will do if he's reelected and tonight he said he will be a dictator on day one. Americans should believe him." No vision at all, Nikki Haley would say.