Mental sufficiency required for last three standing

Bernie Sanders will be 79 on September 8
Joe Biden will be 78 on November 30
Donald Trump will be 74 on June 14

Biden and Trump occasionally sound disconnected and confused in public discussions. Sanders, though generally articulate, is noticeably slower in speech from twenty years ago.

We take it for granted that candidates will get and provide physical health certifications during their presidential campaigns. We do not require, nor do they offer, the same for their mental fitness. As the last three standing, all three owe it to America, indeed the world, to provide certification they are not in mental decline.