Senator Ed Markey, 80, trounced a younger challenger who had made an argument for generational change. Two other longtime Democratic lawmakers hung on, too.

© Mark Stockwell/Associated Press

Representative Stephen Lynch, 71, a centrist, beat Patrick Roath, 39, in a primary that reflected the party’s generational and ideological divides.

© Tierney L. Cross/The New York Times

Senator Edward Markey, who began his congressional career in 1976, faces a challenge from Representative Seth Moulton.

© Mel Musto for The New York Times; Josh Reynolds/Associated Press