So pretend it is Biden.
Reagan was officially diagnosed with Alzheimer’s shortly after leaving office. In all likelyhood, given the nature of the disease he had symptoms long before that. We are seeing older people running for and winning office (and bear in mind there were articles accusing Hillary of dementia and she would be the same age as Trump if she had run). This article actually gives good examples and analysis. Clearly that makes it horribly partisan.
Unfortunately we have no real mechanism for dealing beyond screaming “partisan” and insisting our guy is perfectly normal while the other guy is not.
Dr. Strangelove comes to mind.
As far as I am concerned, the 25th Amendment is still available to deal with such as dementia rendering the "chief magistrate" incapacitated. The list of
Trump's defects is long, and at this time I am not quite sure dementia would add significantly to the incapacity. All the while, we are being treated to
Trumpish pap like this:
"His physical strength and stamina are extraordinary," Bornstein wrote of Trump. "If elected, Mr. Trump, I can state unequivocally, will be the healthiest individual ever elected to the presidency."
No one should ever expect a proper diagnosis to be publicly available.
That points to a far broader problem arising from a President voted into office by the population (I know, Electoral College), and the central role he occupies. Any administration has an incentive to cover up the president's health problems, and that happened in the cases of Roosevelt, Kennedy, and Reagan, and it most assuredly happens with Trump as well. Trump was never fit for office, not on his first day, not now, and at no time in between. In a parliamentary system, the problem doesn't go away entirely, but it's far easier dealt with than in a presidential system. It's really the Founders' most egregious errors, the Electoral College, and the presidential system, that brought about Trump, imply a personality cult - which Trump merely took to a new level - and make it exceedingly difficult to deal with him and those like him.
And then, just look at the answers from the right on this thread, how sycophancy, authoritarianism, personality cult, and undying attachment to the Dear Leader combine to bring about a degree of hatred I haven't seen in all my life. Just imagine what is going to happen in case Pence and Congress use the 25th to depose him. Mind boggling...