BOSTON • Massachusetts U.S. Rep. Joe Kennedy III, a scion of one of America’s most storied political families, is set to announce he will challenge U.S. Sen. Edward Markey in the state’s Democratic primary in 2020.

A person with knowledge of Kennedy’s plans said that Kennedy will formally make the announcement Saturday. The person wasn’t authorized to preempt Kennedy’s announcement and spoke Wednesday on condition of anonymity. The 38-year-old grandson of Robert Kennedy has been quietly laying down the foundation of a run, building up his staff and formally announcing his intentions by filing preliminary paperwork with the Federal Election Commission last month.

“I don’t think primaries are something that people should shy away from,” Kennedy said at the state Democratic convention Saturday.

Kennedy has shied away from directly criticizing Markey, calling him “a good man.”

Joe Kennedy

Carolyn Kaster