Internal polling from Rep. Rod Blum's campaign showed the Iowa Republican leading his Democratic challenger Monica Vernon 52 percent to 36 percent among registered voters in the Hawkeye State's 1st District.
Blum's 16-point edge represents an increase from an internal poll from August that showed him ahead 50 to 43 percent.
The freshman congressman routinely occupies one of the top spots on Roll Call's list of the most vulnerable House incumbents. A member of the House Freedom Caucus, he represents a district President Barack Obama twice carried by double digits.
In the presidential race, Democrat Hillary Clinton led GOP rival Donald Trump 39 percent to 37 percent in the district, according to the latest Blum internal poll. Libertarian Gary Johnson garnered 10 percent and 8 percent of registered voters were undecided.
The Polling Company/WomanTrend poll surveyed 400 registered voters from Sept. 29 to Oct. 1 and had a margin of error of 4.9 percentage points. Seventy percent of surveys were conducted via landline.
Commenting on the survey to The (Cedar Rapids) Gazette, Vernon questioned the poll's sampling and suggested that reliance on landlines doesn't give an accurate glimpse of the electorate.
Blum's poll found the congressman with a 47 percent favorable and 23 percent unfavorable rating. Vernon had a 29 percent favorable and 26 percent unfavorable rating.
Blum, who has tea party support, has been identified as one of the most vulnerable incumbents this year, in part, because of his lack of support from establishment Republicans in this Democratic-leaning district. The National Republican Congressional Committee only recently added Blum to its Patriot Program for vulnerable incumbents and reserved ad time in the district.
He alienated the NRCC by voting against John A. Boehner for speaker after Boehner had campaigned for him in the district in 2014.
Blum ended the Federal Election Commission's three-month reporting period in June with a strong cash-on-hand advantage over Vernon, who had to spend in the Democratic primary.