The candidates have spent the first few weeks of the race sparring over a controversial tax deduction Gomez took in 2005 and a number of checks Markey bounced from the congressional bank that was eventually shut down after an ethics investigation.
The new poll seems to indicate Democratic attacks on Gomez may be working to drive down his popularity.
Gomez is viewed favorably by 42 percent of respondents, while 34 percent view him unfavorably.
Back in early May, about the same number of voters viewed him favorably, but only 27 percent had an unfavorable opinion.
Then, 32 percent of respondents were undecided about Gomez; now, 24 percent aren't sure, indicating that voters getting to know Gomez are unimpressed with what they've found.
Markey, however, has slightly improved his standing with voters. Forty-eight percent view him favorably, up from the 44 percent that felt the same in early May, and 40 percent view him unfavorably, virtually unchanged since the first poll.
Perhaps most troubling for Gomez is the fact that he's losing ground among Democrats, with only 12 percent saying they'd support him, down from the 21 percent of Democrats who supported him in the last poll.
Gomez will need to work to regain some of those Democratic voters if he hopes to win, as Democrats have a strong registration advantage over Republicans in Massachusetts.
However, the Republican does see some good news in the data on independent voters, which are increasingly flocking to support him. He leads among independents 56 percent to Markey's 33 percent, up from a 16 percentage point lead in early May.
More than half of Massachusetts's registered voters are independents, and a strong showing from pro-Gomez independent voters could boost the underdog on Election Day.
Markey's not yet out of the woods. A number of polls have shown Gomez keeping his lead to single digits, a tighter-than-expected margin in the fight for the seat vacated by Secretary of State John Kerry.
Those polls were enough to give national Republicans reason to get engaged in the race, a prospect that's likely to bring with it funding from outside Republican groups.
An influx of millions of dollars from either side could significantly change the dynamics of the race before the June 25 general election date.
The survey was conducted by PPP among 880 likely voters from May 13-15, and has a margin of error of plus or minus 3.3 percentage points.