Democrat Phil Bredesen maintains a narrow two-point lead over Republican Marsha Blackburn in Tennessee's U.S. Senate race, according to a new poll from a Republican-aligned firm that labels the race a "dead heat."

The same poll, conducted by Vox Populi Polling and released Thursday, found that Republican Bill Lee holds a 9-point advantage over Democrat Karl Dean in Tennessee's race for governor.

The poll says 51 percent of Tennessee voters either plan to or are leaning toward voting for Bredesen, a former Tennessee governor, compared to 49 percent for Blackburn, a conservative Williamson County congressman.

Lee, chairman of Franklin-based Lee Co., was the top choice of 55 percent of poll respondents in the governor's race, while 46 percent said they plan to or are leaning toward voting for Dean, a former Nashville mayor.

Related:CNN poll: Bredesen holds 5-point lead over Blackburn; Lee ahead of Dean

The survey, conducted online and via mobile-app-based technology from Sept. 16 to Sept 18, used a sample size of 567 active voters in Tennessee. The margin of error is 4.1 percentage points.

Vox Populi Polling, based in Virginia, was founded in 2014 by a group of Washington Republicans that included Mary Cheney, a political strategist and daughter of former Vice President Dick Cheney, according to Politico.

The firm received a B grade in FiveThirtyEight's recent pollster ratings.

Despite Bredesen's lead, which is within the poll's margin of error, the pollster says Blackburn has a "significant opportunity" to grow her base, pointing to findings that Republicans hold generic support 56 percent to 44 percent among Tennessee voters.

“Tennessee is a must-win state if Democrats have any hope of flipping the Senate this November," said Macy Cambio, PopPolling managing director. "While the fundamentals of the state suggest Blackburn is well positioned going into November, Phil Bredesen is running a tight race in one of the most closely watched contests in the nation.”

More:Fox News poll: Marsha Blackburn has edge over Phil Bredesen in Tennessee's US Senate campaign

The poll's findings came after an NBC/Marist College poll released Sept. 6 also had Bredesen with a 2-point advantage. A Sept. 13 Fox News poll had Blackburn up 3 points while a CNN poll on Sept. 17 found Bredesen up 5 points.

In the new Vox Populi poll, 42 percent apiece said they plan to vote for Blackburn and Bredesen but another 9 percent said they are leaning toward backing Bredesen while 7 percent were leaning toward Blackburn.

More Tennessee voters have no opinions of the gubernatorial candidates

In terms of impressions of the two candidates, 41 percent of respondents had a favorable opinion of Bredesen, 34 percent had an unfavorable opinion and 20 percent had no opinion. Five percent were unaware of him.

Blackburn was found to have slightly lower favorablity numbers, with 38 percent having a favorable opinion of her, 37 percent having an unfavorable opinion and 20 percent having no opinion. Six percent were unaware of Blackburn.

More:Lee with double-digit lead over Dean in NBC/Marist poll

Recent polling in the governor's race has found Lee up anywhere from 9 points to a larger double-digit lead.

While Lee is better perceived than Dean among voters, more voters have no opinion in the race to replace term-limited Gov. Bill Haslam than they do in the U.S. Senate election, which is garnering national attention.

Lee was viewed favorably by 41 percent of respondents in the poll, while 18 percent said they have an unfavorable opinion, 32 percent said they have no opinion, and 9 percent are unaware of him.

Dean was viewed favorably by 31 percent of people in the poll. Eighteen percent said they have an unfavorable opinion of him, 40 percent said they have no opinion and 11 percent said they are unaware of him.

Reach Joey Garrison at 615-259-8236, jgarrison@tennessean.com and on Twitter @joeygarrison.