Tensions ran high 20 years ago as we stood in the well of the Senate before Chief Justice William Rehnquist, all 100 senators and the nation. As House impeachment managers, we presented our case against President Clinton. We were somber but confident, knowing that we had afforded Mr. Clinton every due-process right to defend himself.

Now we find ourselves on the verge of another presidential impeachment. But this time the process is so fundamentally unfair that justice cannot be served. For the past two months, House Democrats,...