Dan Froomkin - Obstruction of Justice, Continued - washingtonpost.com: "The Framers, ever sensitive to the need for checks and balances, recognized the potential for abuse of the pardon power. According to a Judiciary Committee report drafted in the aftermath of the Watergate crisis: 'In the [Constitutional] convention George Mason argued that the President might use his pardoning power to 'pardon crimes which were advised by himself' or, before indictment or conviction, 'to stop inquiry and prevent detection.'
James Madison responded:'[I]f 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. . . ."