One year out from the 2018 Tennessee U.S. Senate race, U.S. Rep. Marsha Blackburn, R-Tennessee, and former Democratic Gov. Phil Bredesen, a potential candidate, have “statistically indistinguishable” approval ratings, a new poll from Middle Tennessee State University has found.

The poll, released Tuesday, found Blackburn is viewed positively by 37 percent of all registered Tennessee voters while Bredesen is viewed positively by 34 percent. Thirty-one percent of respondents said they have negative feelings for Blackburn, while 29 percent had negative feelings for Bredesen.

Blackburn, a conservative congressman from Williamson County, representing Tennessee's 7th congressional district, announced her bid in the Republican primary on Oct. 5 following Republican Sen. Bob Corker’s decision to not seek a third term.

Bredesen, governor of Tennessee from 2003 to 2011, is considering running for the Democratic Party’s nomination. He’s expected to make a decision within a few weeks.

Among just Republican voters, the poll found that Blackburn is leading the GOP primary with positive approval marks from 55 percent of Republican voters. But the survey has a significant omission: former Rep. Stephen Fincher, R-Tennessee, a rival GOP candidate, was not included in the poll.

The poll found conservative activist Andy Ogles has 19 percent approval from Republican voters and perennial candidate Larry Crim has 12 percent approval from GOP voters.

The telephone survey, a sample of 600 registered Tennessee voters, was taken between Oct. 16 and Oct. 23. Fincher, congressman of Tennessee’s 8th congressional from 2011 to 2017, announced his candidacy on Oct. 22.

The poll — which has a margin or error of plus or minus 4 percentage points — tested only positive and negative attitudes of candidates and potential candidates. It did not ask whom Tennesseans plan to vote for.

With party primaries not until August, no candidates have aired ads on television to this point, meaning polling right now is largely a reflection of built-in name recognition of candidates.

Among all Tennessee voters, regardless of party affiliation, Blackburn’s 37 percent approval topped Republican opponents Ogles, 14 percent, and Crim, 7 percent.

On the Democratic side, the poll found 60 percent of likely Democratic primary voters either approve or strongly approve of Bredesen, who has not held public office in more than six years.

James Mackler, a Nashville attorney and former Iraq War veteran — and the lone Democrat to announce a candidacy so far — has approval from 28 percent of self-identified Democrats, according to the poll.

Chattanooga Mayor Andy Berke, who is considering a run, has the approval of 32 percent of self-described Democrats, the poll found.

Among all Tennessee voters, regardless of party affiliation, Bredesen’s 34 percent approval topped the other two Democrats. Berke’s approval is 18 percent among all voters, the poll found, while Mackle is 13 percent.

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