The Issue: How low voter turnout influenced Tuesday’s Democratic primaries in New York City. Barely 17% of Democratic voters citywide — heavily white and under 30 — voted in this primary (“Lefties’ young demographic,” June 25). Those voters may be college-educated, but they’re poorly informed about history. New York is not alone in staying home rather than voting. Nationwide, voter turnout is not nearly what it should be. Republicans too have to…