Recently I was Googling for something else, and I ran across this plot summary in an eight-year-old discussion on the boards on the Straight Dope website. I went through the entire thread on that forum, and nobody ever posted a response that identified the story in question. (I mention this to save you the time of following the link and going to all that trouble yourself.)
Here's what a poster called "Elendil's Heir" said in January of 2010:
I also remember a mid-Eighties book of politically-themed sf short stories. In one of them, an American starship returns after a short but very successful almost-lightspeed voyage. The young captain is hailed as a hero and his many fans beg him to run for President. He isn't yet (biologically) 35 years old, as required by the Constitution, even though to everyone left back on Earth he's pushing 90 if you counted from his birthdate. IIRC the Supreme Court finally decides he can run - so he does, and wins.
That didn't ring any bells in my head, but it sounds like it could be an amusing read. So I'm asking for help in identifying a story I've never even seen with my own eyes! Does anyone think that plot premise sounds familiar?