In the survey, conducted by the National Republican Congressional Committee, Tisei has 47 percent support to Tierney's 35 percent. The polling memo, from NRCC polling director Brock McCleary, asserts that "the allegations of corruption that have haunted Tierney are clearly impacting the Congressman's standing with voters."

That aligns with the Republican attempt to tie Tierney to his family's gambling ring. Though Tierney has said that he knew nothing of the ring, which eventually landed his wife in jail, Republicans hope that if voters associate the congressman with the scandal, they'll be able to nab a tough win in deep-blue Massachusetts.

However, the poll gives President Obama only a 1 percentage point lead over Mitt Romney in the district, and Obama won the district in 2008 by 16 points — an indication that this poll may be skewed in favor of Republicans.

It also gives Sen. Scott Brown (R) a 16-point lead over Democratic challenger Elizabeth WarrenElizabeth Ann WarrenOn The Money: Trump 'ready' for tariffs on all 0B in Chinese goods | Trump digs in on Fed criticism | Lawmakers drop plans to challenge Trump ZTE deal On The Money: Trump rips Fed over rate hikes | Dems fume as consumer agency pick refuses to discuss border policy | Senate panel clears Trump IRS nominee Dems fume as Trump's consumer bureau pick refuses to discuss role in border policy MORE in a race that, in most other polls, remains within the margin of error.

But the polling memo includes the party breakdown of those polled, which is similar to the makeup of Massachusetts. Thirty percent of those polled are identified as Democrats, 13 percent of those polled are identified as Republicans and 57 percent of those polled are identified as independent. In Massachusetts, the 2010 breakdown of registered voters was 37 percent Democratic, 11 percent Republican and 52 percent unaffiliated.

The poll was conducted by Stinson Strategies with 561 respondents and a margin of error of plus or minus 4.1 percentage points.

--This post was published at 1:04 p.m. and updated at 3:03 p.m.