White House social media director Dan Scavino with President Donald...

White House social media director Dan Scavino with President Donald Trump on Thursday. Credit: AP/Evan Vucci

Crackpot theories that defy common sense play a practical and helpful role in President Donald Trump's governance. Sometimes they even serve as audacious versions of "The dog ate my homework."

This week a federal appellate panel dealt Trump an embarrassing blow. Its three judges found the first Twitter president couldn't claim @realdonaldtrump as a private account, given his use of it for official purposes. Therefore he's barred from blocking, and therefore squelching, the voices of his social-media critics as he has tried to do.

Without having a long-parroted conspiracy theory to cite, the president might just come off as a hypersensitive censor who violated free speech in a trivial way. Instead he indulges, along with right-wing allies, in a fishy narrative of how big tech companies plot against them. 

"A big subject today at the White House Social Media Summit will be the tremendous dishonesty, bias, discrimination and suppression practiced by certain companies," he tweeted Thursday, unimpeded.  "We will not let them get away with it much longer."

That's way more entertaining than informing the fan base of how things really work.

Shouting "Conspiracy!" can deflect from a perceived weakness. Remember how an imaginary campaign of massive ballot fraud supposedly cost the winning 2016 candidate the popular vote? 

The fake narrative's biggest plot hole was this: Trump won the Electoral College — which would seem impossible if such anti-GOP fakery had existed. You'd have thought a cabal that could fake "millions" of votes would have gone all the way.

The Mueller investigation spawned another logic-defying "theory" — that it was illegitimately conceived and the work of "angry" partisans. 

Over two years, special counsel Robert Mueller carefully documented Russian efforts to push internet propaganda in support of Trump and the president's later efforts to derail the probe. But Mueller never claimed the president committed crimes.

So now we have this plot hole: Trump & Co. asserted "total vindication" when Mueller's report came out — but they're still pushing claims of a "fixed witch hunt." 

You'd figure this deep-state effort at a "coup" — so darkly intent on taking Trump out — would have said he did something illegal.

But this week, Trump factotum Rudy Giuliani said again on TV: "The reality is that this was a plot from the very beginning to frame Trump, that’s what you’re going to find out." 

Giuliani's tactic is far from unheard of. Defense lawyers are always putting forward "alternative theories" of the crime in question and looking for wrongdoing by the prosecution to get their clients off the hook.

Then there's that Mexico-driven plot, as Trump evoked it, to send criminals, rapists and drug dealers to the United States.

The administration never came close to persuading either party in Congress that a beautiful wall was needed to protect the southern border.

Nor did its other strategies stave off what became a rush of desperate refugees through Mexico. Nor did the president show effort to negotiate his way toward sensible immigration reform.

Avoiding an admission of failure now requires projecting an image of sheer madness on others. The press, tweets the president, “is writing phony and exaggerated accounts.” Democrats seek "open borders" in a plot to overwhelm America.

Remember: We are not watching a marginal group of crazies rant about vaccines, chem trails, the moon landings and fluoride. This is the sight of entrenched power creating excuses for its shortcomings.