Bruce Ackerman, at Yale Law, sent this heads-up and it is well worth reading:
Politico (January 25, 2020)
Trump’s Lawyers Are Getting Andrew Johnson’s Impeachment All Wrong
Yes, the 17th president was acquitted on similar charges—but bribery likely played a role.
By bribery, Ackerman means bribery played a part in swinging the crucial vote to acquit Johnson. It’s well worth reading:
https://www.politico.com/news/magazine/2020/01/25/trump-impeachment-andrew-johnson-104066