The bully-in-chief keeps issuing taunts on Twitter that accuse former President Barack Obama of some unspecified grand conspiracy. In what may be more evidence of a deteriorating mental state, President Donald J. Trump has made up "Obamagate," apparently to account for the incompetence and malfeasance of his own administration.

On Thursday, Trump tweeted out a call for his congressional lackeys to force President Obama "to testify about the biggest political crime and scandal in the history of the USA, by FAR ... Do it, @LindseyGrahamSC, just do it."

But even the lackeys seem to understand this is another example of the president's inability to stop heaping damage upon himself. While White House aides have not been able to stop Trump from appearing at coronavirus "briefings," where he dishes out dangerous advice, distorted data and downright lies, Republican senators are quite unlikely to try to subpoena Obama. That would bulldoze what remains of Trump's re-election campaign.

Indeed, telling a reporter he would not attempt to call Obama before the Senate, Graham added: "I understand President Trump's frustration, but be careful what you wish for."

As humorist Andy Borowitz has noted, Obama speaks in complete and coherent sentences. That alone presents a sharp contrast to Trump, whose answers to impromptu questions wander into a thicket of unconnected words and thoughts and who has trouble even reading from a teleprompter.

Besides, Republicans don't want to give Obama uninterrupted hours of televised hearings to outline all the outrageous goings-on in the Trump administration, including -- but certainly not limited to -- Trump's disastrous handling of the coronavirus crisis. Officials of the Obama administration handed their successors a 40-page, color-coded document on handling pandemics, which the Trump folks ignored. (Earlier this month, in an online discussion hosted by the Trump re-election campaign, Mitch McConnell told the lie that the Obama administration didn't leave them a "playbook" for the pandemic. The Washington Post rated that a three-Pinocchio whopper.)

Obama has wisely reserved his political capital, endorsing his former vice president, Joe Biden, only after it was clear that Biden would become the nominee, and keeping mostly quiet about the Trump administration. And Biden, also wisely, plans to make Obama a centerpiece of his campaign. You'll be seeing a lot more of the former president in televised appearances and on the campaign trail, making the case for Biden and against Trump.

But Trump, according to published reports, also plans to make Obama a centerpiece of his campaign. That makes a lot less sense. There is no doubt that the racists, conspiracy-hucksters and crazies who make up a reliable portion of the Republican base are prepared to believe whatever Trump says about Obama, no matter how outlandish. There are not enough of them, however, to fashion a winning coalition. The presidential election will be a referendum on Trump, not Obama.

The former president clearly got under Trump's skin -- very easy to do since Trump is so thin-skinned -- when he characterized Trump's handling of the pandemic as an "absolute chaotic disaster" in a private phone call with 3,000 of his supporters recently. Given the number of people on the call, Obama had to be aware that the call would likely be leaked.

The leaked audio, though, merely agitated a festering sore deep in Trump's psyche. He is obsessed with his predecessor.

Racism probably plays a part. Trump entered the political stage as a prominent birther, furiously repeating the lie that Obama was not born in the United States and was therefore an illegitimate president. And that implicit belief that no black man should ever have been president may have further stressed Trump's already-wounded ego since Obama was clearly a much superior president.

As the death toll mounts and the economy limps along on fumes, Trump seems to be decompensating, to use the psychiatric term -- spiraling out of control, indulging crazier conspiracies, lashing out more often at presumed enemies. If Obama's comments in one phone call could prompt Trump to call for his predecessor to testify about made-up "crimes," then Obama's coming appearances on the campaign trail could spark -- well, we'll see. This campaign will obviously be one for the history books. It could be one for the psychiatric annals, as well.