Incumbent Sen. Ed Markey maintains a commanding lead in the Massachusetts Democratic Senate primary due to strong recent polling gains, broad support among progressives, women, and liberals, and higher voter trust on key issues ahead of the Sept. 1 vote. Multiple August surveys, including those from Suffolk University/Boston Globe and UMass Amherst, show Markey ahead by double digits after the race tightened earlier in the summer, reflecting effective grassroots organization and incumbency advantages in a state where Democrats dominate. Rep. Seth Moulton's generational challenge and calls for new leadership have not closed the gap despite debates and advertising. Other declared candidates have largely withdrawn or endorsed Markey. A late surge in turnout favoring moderates or independents, or unexpected developments before primary day, represent the main paths to narrowing the margin in this low-uncertainty contest.