If you wondered why Trump is suddenly talking a lot about autopens, here’s why. He has ordered an investigation of Joe Biden’s mental state while in office, partly as a witch hunt against the former president and his aides, but also as an attempt to invalidate every action of Biden’s presidency.

The New York Times provides the context:

In an executive order, Mr. Trump put the power and resources of the federal government to work examining whether some of Mr. Biden’s presidential actions were legally invalid because his aides had enacted those policies without his knowledge.

The executive order came after Mr. Trump shared a social media post over the weekend that claimed Mr. Biden had been “executed in 2020” and replaced by a robotic clone, following a pattern of suggestions by the president and his allies that Mr. Biden was a mentally incapacitated puppet of his aides. …

A central claim of the conspiracy theory, as described by Mr. Trump himself, is that Mr. Biden’s use of the autopen system—which reproduces a person’s signature to be affixed to official documents—can legally invalidate those documents.

Mr. Trump has claimed, for example, that some pardons Mr. Biden had made during his time in office were invalid because they were signed using an autopen. (There is no power in the Constitution or case law to undo a pardon.)

Trump seems particularly interested in preemptive pardons issued by Biden to his aides, members of Congress, and other officials to shield them from Trump’s retribution. By searching for a pretext to declare these pardons illegitimate, he hopes to clear the way for politically motivated prosecutions.