While former President Donald J. Trump’s indictment in Florida over his retention of classified documents came at relative warp speed for the Justice Department, the criminal inquiry into his efforts to overturn the results of the 2020 election was slower to unfold.
But that investigation accelerated quickly after the appointment last November of a special counsel, Jack Smith, who has overseen a small team of veteran prosecutors inherited, for the most part, from an existing investigation into the Jan. 6, 2021, attack on the Capitol that had been based in the United States attorney’s office in Washington.
A central player has been Thomas P. Windom, a veteran prosecutor known for a successful case against members of a white supremacist cell in Maryland. He was quietly brought on in late 2021 — nearly a year before Mr. Smith’s appointment — when it was clear the inquiry would inevitably lead to Mr. Trump.
Working under the close supervision of aides to Attorney General Merrick B. Garland, Mr. Windom began to methodically seek information about the roles played by some of Mr. Trump’s top advisers, including Rudolph W. Giuliani, Jenna Ellis and John Eastman, with a mandate to go as high up the chain of command as the evidence warranted.
He continued in that role after Mr. Smith’s appointment and has become a familiar figure at a federal courthouse that has been the venue for dozens of cases concerning the Capitol riot, including Mr. Trump’s. (A little too familiar to some: Last month, a federal judge hauled Mr. Windom out of a Trump-related proceeding, upset that he had prevented a lawyer representing a witness in front of a grand jury from appearing in his courtroom.)
Another key player — and someone Mr. Smith knew from his days as chief of the department’s public corruption unit — is J.P. Cooney, a veteran of the public corruption division of the U.S. attorney’s office in Washington.
Mr. Cooney, in particular, is known for his aggressive approach. He unsuccessfully prosecuted two Democrats — Senator Bob Menendez of New Jersey and Gregory B. Craig, a White House counsel during the Obama administration — and investigated Andrew G. McCabe, the former F.B.I. deputy director, whom Mr. Trump vilified for the bureau’s investigation into ties between Mr. Trump’s 2016 campaign and Russia. (Mr. McCabe was never prosecuted.)
In early 2021, Mr. Cooney pressed federal law enforcement officials to turn their attention to people in Mr. Trump’s orbit, including his flamboyant political adviser Roger J. Stone Jr., according to The Washington Post. He would eventually work on the successful prosecutions of Mr. Stone and another Trump adviser, Stephen K. Bannon.
He joined Mr. Windom’s team in mid-2022, then moved into Mr. Smith’s office late last year.
The assistant U.S. attorney in federal court on Tuesday, when a grand jury handed up a four-count indictment against Mr. Trump, was Molly Gaston, who has worked closely with Mr. Cooney on the Stone and McCabe cases.