Six Democratic primaries for the Massachusetts Senate are scheduled for September 1, 2026. All 40 seats are up for election in the chamber, in which Democrats have a 35-5 majority.

All six of those primaries qualified as battlegrounds under Ballotpedia’s battleground primary criteria. Two are open-seat contests — the 2nd Middlesex District and the 5th Middlesex District — while the other four feature incumbents facing credible challengers.

Two of the incumbent primaries feature incumbents facing multiple challengers. In the 1st Suffolk District, incumbent Nick Collins (D) faces Latoya Gayle (D) and Juwan Skeens (D). In the Norfolk, Plymouth, and Bristol District, incumbent William Driscoll Jr. (D) faces Tony King (D) and Michael Zullas (D). The other two incumbent primaries each feature one challenger: Persis Yu (D) is challenging Michael Rush (D) in the Norfolk and Suffolk District, and Daniel Lander (D) is challenging William Brownsberger (D) in the Suffolk and Middlesex District.

Two of the battleground primaries in the 1st Suffolk District and Suffolk and Middlesex District feature splits among prominent Massachusetts Democrats and Democratic-aligned groups.

• 1st Suffolk: Boston Mayor Michelle Wu (D) endorsed Gayle. Several current and former state legislators and municipal officeholders endorsed Collins.
• Suffolk and Middlesex: Wu and U.S. Sen. Elizabeth Warren (D) endorsed Lander. Gov. Maura Healey (D), Lt. Gov. Kim Driscoll (D), and Attorney General Andrea Joy Campbell (D) endorsed Brownsberger.

MassLive's John L. Micek wrote, "Whether Bay State voters choose insurgent candidates or stick with well-known name brands reflects a broader tension within the Democratic Party, where loyalists are wrestling with similar questions about generational change."