Our fake president, a child at play, was elected with 27% of voting-age eligible Americans

Sources:  United States Electrion Project (Voting age eligible/registered voters)

Related reading:
Who are the three-quarters of adult Americans who didn't vote for Trump?  (The Guardian US, 1/18/2017) 
Trump was elected by a little more than a quarter of eligible voters.  (Vox, 11/10/2016)