But not this year, when a growing anti-incumbent fervor seems to be gripping the country, dealing blows to Democratic House members and Republican senators alike during a bruising primary season. So far this year, 10 House members — seven Democrats and three Republicans — along with two Republican senators have fallen, for a total of 12 defeated incumbents. Larson was defeated in his Democratic primary by Luke Bronin, who is decades younger and the former mayor of Hartford. Democratic incumbents have had a rough stretch of their own in the House this year. Before Larson’s loss Tuesday, four Democratic incumbents had lost their primaries in reliably blue districts in cities including Denver, Detroit and New York to more liberal opponents, many of whom identified with democratic socialism.