What you need to know about Tuesday’s most interesting primary election

Tuesday’s most interesting election is the primary in Massachusetts’ 7th congressional district, where incumbent Rep. Mike Capuano (D) faces a primary from Boston City Councilor Ayanna Pressley.

In some ways, the race mirrors a number of other high-profile contested primaries — including Alexandria Ocasio-Cortez and Cynthia Nixon’s races in New York, as well as Andrew Gillum’s in Florida — as Pressley, a younger woman of color, has mounted a chall...