Democrats are out with another optimistic poll in a battleground House race in Massachusetts, but the contest for Rep. John Tierney's seat is far from settled, with a dozen conflicting surveys offering little clarity.

House Majority PAC, the major Democratic House super PAC, released a poll by Democratic pollster Garin-Hart-Yang showing Seth Moulton with an 11-point lead over Republican Richard Tisei. Moulton received 47 percent to Tisei's 36 percent, while independent candidate Chris Stockwell received 9 percent, and 8 percent were undecided.

The poll was conducted Oct. 16-17, surveyed 406 likely voters, and has a margin of error of plus or minus 5 percentage points.

The super PAC conducted a poll in late September that received similar results: Moulton led 43 percent to 33 percent. But the overall polling picture of the race is anything but settled. Republicans have released three polls in the last month showing Tisei with either a 1- or 2-point lead, and Emerson College has released two automated nonpartisan polls showing the results within the polls' margins of error this month.

Moulton, a Marine Corps veteran, upset Tierney in the September Democratic primary, largely on the grounds that he would fare better against Tisei, a former state senator who almost unseated Tierney in 2012. Tierney has dealt with bad press over his wife and brother-in-law going to jail on charges of running an illegal offshore gambling operation.

Democrats are confident in Moulton, who has less baggage than Tierney did. Last week, the Democratic Congressional Campaign Committee canceled $430,000 in airtime supporting Moulton, shifting those funds toward two New Hampshire Democrats who appeared to need more help.

But Republicans point to polls showing Moulton and Tisei neck-and-neck—and to Moulton's hardball campaign tactics—as evidence Tisei could still flip the seat from blue to red. Moulton's campaign released a TV ad Monday accusing Tisei of voting against veterans benefits, citing Tisei's vote against an entire state budget in 2009 that included funding for veterans benefits, among many other programs. Tisei campaign spokesman Charlie Szold said Moulton's campaign would not have run the ad if he had such a wide lead.

"These groups and Seth Moulton aren't acting like they believe their own polls," Szold said. "What we're seeing is showing this race neck-and-neck and will remain so until Election Day."

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.