If there were a real impeachable offense, there would be no fretting about witnesses at the trial. Senate leaders would be contemplating that, after hearing the case extensively presented by both sides, there might well be enough votes to convict without witnesses. But if there were an appetite for witnesses, witnesses would be called . . . as they were in Watergate. And just as in Watergate, if the president withheld vital evidence of appalling lawlessness, the public would not be broadly indifferent to administration stonewalling.
If there were an obviously impeachable offense, the garrisons of Fort Knox could not have stopped Nancy Pelosi from personally marching impeachment articles into the Senate the second the House had adopted them — in what would have been an overwhelming bipartisan vote (of the kind that Pelosi, not long ago, said would be imperative for a legitimate impeachment effort).
The Framers expected presidents to abuse their powers from time to time. And not just presidents. Our Constitution’s theory of the human condition, and thus of governance, is that power is apt to corrupt anyone. It needs to be divided, and the peer components need to be incentivized to check each other. The operating assumption is that, otherwise, one component would accumulate too much power and inevitably fall prey to the tyrannical temptation. But as Madison observed, men are not angels. Separation of powers arms us against inevitable abuse, it does not prevent abuse from happening. Abuse is a given: Congress uses lawmaking power to encroach on the other branches’ prerogatives; judges legislate from the bench, presidents leverage their awesome powers for political advantage. The expectation is not that government officials will never overreach; it is that when one branch does overreach, the others will bring it into line.