The Belknap impeachment precedent is tainted with racism. All Southern and Border State Democrats voted to impeach and convict him. Why? It was 1876 and their goal was to mire the Republicans in political scandal, win the election, and get Federal troops pulled out of the South. Only then would they be able to fully impose Jim Crow segregation, deprive Black Americans of their rights, and let the KKK run wild. Besides Secretary of War William Belknap was guilty of incredible corruption. So if the Constitution had to be stretched, it was no big deal for those who had fought against the Union a decade earlier. Your best precedent is dripping with racism. It was not the dispassionate consideration of Constitutional principles you make it out to be. https://link.medium.com/29EzhORALdb
You neglect to mention the most directly relevant precedent, the impeachment of President Nixon that was stopped soon after he resigned. There was bipartisan sentiment he was guilty of criminal and impeachable offenses. But most people at the time believed that it was improper and unconstitutional to continue Nixon’s impeachment after he was out of office. Many people wanted Nixon to be tried in criminal court and it was only President Ford’s pardon that prevented that. The scholars at the time viewed Belknap as a flawed precdent. Try to explain why the Nixon precedent doesn’t apply.