Voting while far from home is generally accomplished by filling out and submitting an absentee ballot. It turns out, that’s pretty much how it works even if you’re in space.

 Voting while far from home is generally accomplished by filling out and submitting an absentee ballot. It turns out, that's pretty much how it works even if you're in space.  The process for astronauts starts about a year before they depart on their scheduled missions.  At that time, they pick which of the federal, state, and local races they'll be participating in while in space. Then, about six months prior to election day, the astronauts are provided with the standard "Voter Registration and Absentee Ballot Request – Federal Post Card Application."  That system was established in 1997, and, that very same year, NASA's David Wolf became "the first American to vote in space while on the Russian Mir Space Station."