Andrew Secretary of the Treasury to Harding, Coolidge, and Hoover. In 1932 when FDR took over he decided to destroy Mellon. So they charged him with tax fraud and put him on trial that spanned multiple years. They didn't even allege actual fraud, they were trying to say that tax avoidance, legal tax avoidance, was equivalent to law breaking and get him jailed for it. They also forced him to lay out all of his financial dealings in public. Just a fishing expedition and it failed, Mellon was acquitted.
But the idea stands: Get the returns, find something that, even though legal they can say should be illegal, and impeach Trump. Then make it a public spectacle to go over ever record of every deal he ever did.
FDR was an evil SOB.