Mr. Campos’s scheme began several years after Mrs. Bush died in 1992, when he told the Bushes that he had come up with a novel way of honoring her — with a small museum, in her name, within the train station here, where she had once arrived on the passenger train the Orange Blossom Special. For funding, he turned to the new Republican administration in Tallahassee, headed by Jeb Bush, Mrs. Bush’s grandson.

Image Tony Campos after his arrest on a parole violation in February. For his proposed museum, Mr. Campos turned to state grants, which he was later accused of misusing. He pleaded guilty to grand theft in 2013. Credit... Miami-Dade Corrections Department

Over seven years, the State of Florida awarded about $1.2 million in a series of grants to support putting together the museum as well as restoring historic rail cars, complementary displays that Mr. Campos promised would be inaugurated in an opening ceremony at which the Bushes would be honored guests.

But the museum was never built, the rail cars languished, and about the time Mr. Bush left office in 2007, law enforcement agencies began a criminal investigation into Mr. Campos. He eventually was charged with multiple felonies and accused of misusing hundreds of thousands of dollars in state funds. In 2013, he pleaded guilty to grand theft.

Mr. Bush, who had earned a reputation as a fierce opponent of wasteful government spending, had to explain to detectives who interviewed him that he had no role in the grants, while insisting that he only superficially knew Mr. Campos, according to a summary of the meeting contained in a voluminous batch of state records pertaining to the case.

Those records also suggest that while Mr. Bush never explicitly endorsed using state money for the project, he did not stop the funding, either. Instead, a grant manager for the state told investigators, the message from supervisors was: “Whatever Campos wants, make sure he gets it, because he could cause them a lot of problems and was politically connected to the right people.”