New Jersey will begin allowing many 17-year-olds to vote in primary elections two years from now under a law Gov. Phil Murphy signed Thursday. The measure permits Garden State residents who are 17 to cast ballots in primaries — the races that determine political parties’ nominees — as long as they turn 18 by the general election, starting in 2026. New Jersey joins 19 other states and Washington, D.C. with similar laws. Murphy, a Democrat, signed the Democratic-sponsored bill — known as the “New Voter Empowerment Act” — seven years after his Republican predecessor, Gov. Chris Christie, vetoed a…