Brentwood resident Judy Partain is planning to cast a ballot for Republican senatorial nominee Marsha Blackburn in this year's midterm elections, despite having an appreciation for former Democratic Gov. Phil Bredesen.

“I liked what Bredesen did as governor, and if he wasn’t a Democrat, I’d be voting for him,” she said, adding that the GOP must maintain control of the Senate.

And although Partain has reached her decision, she is part of a key demographic that could decide the fate of this year’s U.S. Senate race: suburban voters.

Experts on both sides of the political aisle are eyeing how voters in the outskirts of Tennessee’s major cities may help tilt the balance in the campaign to replace retiring U.S. Sen. Bob Corker.

"We know that President Trump is relatively weaker in well-educated suburban areas than have been other Republican candidates for president," said Whit Ayres, a Republican pollster and president of North Star Opinion Research.

Indeed, Trump won Tennessee overall by 26 percentage points in 2016. He carried some rural counties with more than 80 percent of the vote. But in suburban areas, his support wasn't as strong.

Ayres said in 2016, Republicans traded large, fast-growing upscale counties for slow-growing downscale counties.

"It worked for Donald Trump in 2016 by the hair of his chiny, chin chin. But it's not a formula for long-term success," he said.

More:Phil Bredesen holds slight edge over Marsha Blackburn in new NBC/Marist poll

Take for example Franklin, where Trump's margin of victory over Hillary Clinton was narrower. In fact, in two precincts near downtown Franklin, Trump won by fewer than 100 votes, according to a recently published map from The New York Times detailing precinct-level results nationwide from the 2016 election.

Likewise, in some precincts near Murfreesboro, Trump won by less than 10 percentage points. The same holds true in the Memphis suburbs near Germantown and in the suburbs around Knoxville.

They are areas where voters like Murfreesboro resident Lindsey Robertson live. Although she is still researching the candidates, she could see herself voting for Bredesen.

Robertson, who voted for Trump in 2016, said she prefers to vote for someone based on issues.

Noting that she’s a registered nurse who opposes the legalization of marijuana for recreational use, Robertson said there are certain things that Blackburn supports “that I don’t.”

Polls show suburbs, women key for Bredesen

And Robertson is not alone in her openness to considering Bredesen.

A recent poll from NBC News and Marist College found 52 percent of suburban respondents said they would vote for Bredesen, compared with 43 percent for Blackburn.

Ayres said another demographic that the president, and Republicans more generally, have struggled to attract are college-educated women.

“(They) are the weakest of the demographic categories among whites for Trump and for Republicans, unless the candidate appeals to them,” he said.

Seizing on the state's political landscape in the suburbs, Bredesen has worked to attract and show his support from women. In recent months, he’s hosted roundtable discussions throughout the state, specifically aimed at talking with women about health care.

Last week his campaign announced “Women United for Bredesen” — a group the campaign boasts has 50,000 Tennesseans aimed at providing a “space for women” to organize and highlight issues important to them.

“It’s no secret that suburban women, you know, are probably one of the keys," Bredesen said in an August interview with the USA TODAY NETWORK - Tennessee.

Blackburn — who is hoping to become the first woman in Tennessee elected to statewide office — has seldom talked about her gender. Last month Blackburn launched an ad noting her opposition to sex trafficking.

More:Blackburn highlights fight against human trafficking in latest ad

Abbi Sigler, her campaign spokeswoman, recently told The Associated Press that Blackburn will “continue to fight for Tennessee women and families.”

A critical seat

The divide between the two candidates among female voters may already be emerging, with less than two months to go until the Nov. 6 election.

The NBC News/Marist poll found 55 percent of college-educated white women said they would vote for Bredesen. Just 40 percent of such respondents said they would vote for Blackburn.

Holly McCall, chairwoman of the Williamson County Democratic Party, said she’s constantly hearing from women who want to volunteer for Bredesen’s campaign.

McCall, who grew up in Williamson County and has seen it shift politically over time, said she remained optimistic that Democrats are turning the tide in an area dominated by the GOP in recent years.

“There does seem to be a shift towards the center in the last couple of years,” she said, noting that Williamson County was the only county in the state to not vote for Trump in the 2016 Republican primary.

“When the Republicans try to tar him with some of the tags that they like to put on Democrats, like a Nancy Pelosi or Chuck Schumer Democrat, people know Phil Bredesen and they just don’t believe that,” she said.

Ayres said in order for Blackburn to succeed, she will need to remind voters of what would happen if Democrats take control of the U.S. Senate. Tennessee is among a handful of states seen as a battleground in the midterm elections.

“It’s the task of the Marsha Blackburn campaign to persuade them," he said, "that if they vote for Bredesen that may be the critical seat that gives the majority to Democrats."

It's that exact reason, Partain — the Brentwood Republican — said she planned to vote for Blackburn.

Scott Broden contributed to this report.

Reach Joel Ebert at jebert@tennessean.com or 615-772-1681 and on Twitter @joelebert29.