PolitiFact is reporting that it fact-checked the third and final debate in the Massachusetts Democratic primary for U.S. Senate between Sen. Ed Markey and U.S. Rep. Seth Moulton. The fact-checking was conducted with partners WCVB-TV, WBUR-FM, and The Boston Globe.

During the debate, Moulton directed viewers to his website to find "independent fact checkers" on Markey's statements. PolitiFact said it reviewed the site but found only Federal Election Commission links, not independent journalistic fact-checks.

Regarding technology legislation, Moulton criticized Markey for co-authoring the 1996 Telecommunications Act, which he linked to a lack of accountability for big tech and harm to children online. Markey responded by citing his authorship of the 1998 Children’s Online Privacy Protection Act (COPPA) and a new Youth AI Privacy Act. PolitiFact said Markey did co-author the 1996 act, which includes a provision shielding social media platforms from liability for user-posted content. It also said Markey authored COPPA, which established data protection for children under 13 and is responsible for the common 13-year-old age minimum for online accounts. However, PolitiFact clarified that COPPA does not allow parents to sue tech companies for harm; only federal regulators and state attorneys general can bring such lawsuits. Markey's Youth AI Privacy Act, introduced in March and passed a Senate committee Aug. 5, aims to regulate chatbots interacting with minors.

The candidates also debated their stances on the Iran war, which President Donald Trump started, and defense spending. Markey claimed Moulton voted against a Senate impeachment resolution after the June 2025 bombing of Iranian nuclear facilities and for a "trillion-dollar defense budget" in December 2025. Moulton countered that he is a House member, not a senator, and therefore did not vote on a Senate impeachment resolution. He also stated he voted against the defense bill after the Iran war began and that Markey voted to start the Iraq War. PolitiFact said the House held two impeachment votes since Trump's second term, both before the Feb. 28 Iran war. It said Moulton voted to dismiss an impeachment motion in June 2025 and against dismissing a new measure in December 2025, aligning with House Democrats in both instances. PolitiFact clarified that Markey's claim about Moulton's defense budget vote was "cherry-picked," noting Moulton voted for a December 2025 authorization bill, which addresses policy, not direct funding. It said Moulton voted against appropriations bills containing defense spending in January, February, July 2025, and a subsequent authorization bill in June. PolitiFact confirmed Moulton is correct that Markey voted to authorize the Iraq War in 2003, a vote Markey later called a "mistake."