Imagine the following situation: The House of Representatives conducts an impeachment investigation into the president. A House committee subpoenas witnesses to provide damaging evidence. What if the president, any president, were secretly to suggest to these witnesses that he will pardon them if they are convicted of contempt for refusing to testify or for committing perjury while testifying? Under a strict reading, use of the pardon power in this context would be constitutionally authorized: The president would not be overturning an impeachment conviction.
In this manner, the president could undermine impeachment by inducing witnesses to perjure themselves. This practice would go far to achieve the result the framers most feared: unchecked power in the hands of the executive. Of course, courts would presumably still enforce separation of powers, and the president would still be subject to an electoral check. Nevertheless, a president effectively freed from the check of impeachment would represent a dangerous alteration in the balance of governmental power.
Presidential suborning of perjury is itself most likely an impeachable offense. But the impeachment remedy for such presidential misdeeds may well prove to be insufficient for checking a president’s guerrilla warfare on the impeachment process.