age is an issue because it implies an increasing likelihood towards senility. for that reason alone, you can't brush off "ageism" the way you'd brush off racism or sexism - age does matter, if only on the extremes.

i'm less concerned about dole or mccain as precedent and more concerned about reagan, who it is well understood began to lose it near the end of his term - and was eventually officially diagnosed with alzheimers.

we're talking about an extremely important job, here, that can't tolerate any kind of mental slowness. i would consequently actually support a constitutional amendment to put an age limit somewhere around 75 - which is where mandatory retirement kicks in on the canadian supreme court.

http://nymag.com/intelligencer/2019/02/will-age-be-an-issue-in-the-2020-presidential-race.html