It can be hard to grasp the point of all this. The point is that Mr. Trump is a great patriot who did nothing wrong, while the Democrat he views as the biggest threat to his continuing legal immunity is an illegitimate traitor. You see, if Mr. Mueller’s entire investigation was nothing but the continuation of a fabulously intricate conspiracy theory meant to undermine America’s democratic sovereignty, then Mr. Trump had to obstruct it to defend the republic. If Joe Biden was centrally involved in it, then he’s the corrupt threat to democracy. It’s a paranoid piece of fiction that would make Thomas Pynchon, or Vladimir Putin, proud.

This is the lunacy behind Mr. Trump’s willingness to casually endanger Ukraine’s ability to defend itself against Russia. Worse, by ordering the attorney general, the secretary of state and his personal fixer to lend counterfeit substance to this ridiculous effort, he has untethered American diplomacy and law enforcement from reality.

If the House goes through with impeachment but the Senate acquits, Mr. Trump’s lawlessness will have been lavishly rewarded. He will take it as a signal that absolutely anything goes — especially given the Senate’s failure to act in any meaningful way on election security. Should he win, a sizable majority of the public will see it as an electoral coup and deny the validity of his claim to power. It’s easy to imagine enormous mass protests that bring Washington to a halt, dangerous indeterminacy in the continuity of government, and worse.

If Senate Republicans hold their majority through an election that stinks of corruption, they’ll be dogged by the same crisis of legitimacy. If they nevertheless go on to use their dubious authority to continue stacking the courts and shielding the president from accountability, Americans won’t be wrong to conclude that our democracy has crumbled and that the United States has devolved into one of the world’s many soft-authoritarian kleptocracies claiming popular legitimacy from behind a cheap veneer of rigged elections. It can definitely happen here.

Senate Republicans who would vote in secret to remove Mr. Trump need to finally come to the defense of their country and do it in public. The odds of Republicans holding the Senate in a clean race are strong. But senators who choose to ignore the duties of their office in order to protect Mr. Trump will communicate with ringing clarity that they don’t care about having a fair election; that they don’t care whether the American people have really granted them the authority to govern; and that they think their own voters don’t care about any of this, either.

But the American people, Democrats and Republicans alike, do care. The fainthearted lions of the Senate ought to bear in mind that a defiant citizenry inflamed by indignation and jealous of its rights can overwhelm a corrupt regime’s dirty electoral plans. An election with an impeached Donald Trump at the top of the Republican ticket is an invitation to an electoral uprising that should haunt Mitch McConnell’s dreams.

Senate Republicans owe us the courage of their private convictions. If they can’t find it, they should at least be wary of assuming that cultlike devotion to the president will allow them to weather the coming storm, or that, in the end, they will be rewarded for a faithless calculation to regard their constituents with contempt.

Will Wilkinson (@willwilkinson) is the vice president for research at the Niskanen Center.

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