“Biden dementia” is made up. He’s a typical 79 year old, has some forgetful moments and isn’t good for 70-hour week, but he’s not going anywhere on account of his cognitive health. His bigger risk is stroke or heart attack or a fast metastasizing cancer - and those are real risks for sure, killing or disabling lots of 79 year old in a 5 year timeframe.
“Harris unpopular among Democrats” is also made up. A black woman who hasn’t gone so far off the socialist deep end to lose corporate support is untouchable. She is not being dropped from the ticket or pushed aside from the (acting) Presidency or the 2024 Presidential nomination if Biden’s health dictates or 2028 nomination under any circumstances. We’re stuck with her for better or worse.
Most of the 79 year old's that I know can still think clearly, express themselves well and move with a smooth, steady gait. So, no, I don't think that the dementia assertion, as it applies to Biden, is made up.