Founding Father James Madison, at the Virginia ratifying convention for the Constitution, on impeachable offenses:
“[I]f the President be connected, in any suspicious manner, with any person, and there be grounds tp believe he will shelter him, the House of Representatives can impeach him; they can remove him if found guilty…”
Madison also said:
“If the President be connected, in any suspicious manner with any person, and there be grounds to believe he will shelter him, the House of Representatives can impeach him; they can remove him if found guilty.” Using the power of the presidency to “pardon crimes which were advised by himself” or to “stop inquiry and prevent detection” of crimes is an impeachable offense.
This seems plain enough to me. Somebody should tell Conyers.