Though the incumbent is largely believed to be safe, as he's running in a red-leaning district that favors Mitt Romney, the race remains in flux. Recent investigations into the possibility that he ran a shadow campaign in support of Garcia's challenger have blanketed newspapers in the area, and Garcia's campaign asserts that the bad press is taking a toll on Rivera's campaign.

But this new poll indicates Rivera still maintains a lead, with 44 percent support to Garcia's 38 percent support. The poll gives him a 38-percentage-point lead among Cuban-American voters in the district as well. That bloc could make a big difference come November — the a state has a large Cuban-American population, which votes reliably Republican.

Garcia's campaign spokesman Jeffrey Garcia, however, dismissed the poll, arguing that the basic levels of turnout upon which it was premised were flawed.

"Romney is trailing bad in the two counties in our district or the constant barrage of bad news and scandals surrounding Rivera that are reported on almost daily in our local media," he said in an email.

The poll was conducted in both English and Spanish with 422 likely voters from Sept. 13-16.

--This article was published on Sept. 20 and updated on Sept. 21.