COLUMBUS, Ga. — If Democrat Michelle Nunn wins Georgia’s open Senate seat in November, she will undoubtedly have experienced countless scenarios similar to one on a cold and windy mid-April morning on this city’s revitalized Chattahoochee riverbank.

Patty Cardin, a local retiree and Mitt Romney voter, walked alongside Nunn, peppering the Senate candidate with questions about her father. Cardin, who said she came away impressed, wouldn’t be the last Romney supporter lured to a Nunn campaign event that day by the legacy of former four-term Democratic Sen. Sam Nunn.

It’s the blend of that reverence for the candidate’s father with appreciation for Nunn’s own message of business-friendly bipartisanship that’s positioning the former head of the Points of Light Foundation to peel off a chunk of moderate Republicans in November. That’s vital in Georgia, where Democrats have struggled statewide for more than a decade — but it’s also just a piece of Nunn’s uphill path to victory.

And with so many vulnerable Democratic Senate seats this cycle, this GOP-held seat could play a pivotal role in deciding the majority.

“It does involve getting people mobilized in a non-presidential year and excited about the race, and getting lots of people out there,” Nunn said in an interview in the living room of a south Georgia home, just after delivering a 10-minute stump speech to some 50 supporters.

“And certainly converting some people that have been independents or voting Republican, and sort of demonstrating to them that they can have the kind of leadership that they’re looking for in an independent-minded Democratic candidate,” she continued.

In a trio of recent campaign events and in her first two TV ads, Nunn has worked to accomplish the latter. She had another strong fundraising quarter in which she raised $2.4 million, ending March with $3.9 million on hand, making state and national Democrats optimistic about Nunn’s ability to define herself before Republicans can choose a nominee.

Behind the scenes, a coordinated effort between Nunn and gubernatorial candidate Jason Carter, the grandson of President Jimmy Carter, is based in a growing number of offices in the state, where senior field operatives are building the groundwork for a voter registration and contact operation.

As Senate Democrats work to make the midterm electorate in battleground states more closely resemble a presidential cycle, they have to do better than that in Georgia, where President Barack Obama lost by 7 points without putting up much of a fight.

A boom in the metro-Atlanta population over the past decade included a spike among minorities, who are generally more likely to support Democrats. And while the percentage of the white vote decreased from 75 percent to 61 percent from 2000 to 2012, Democrats in the state say there are still more than 800,000 unregistered black, Hispanic and Asian voters.

When asked why Democrats expect to register black voters who stayed home twice when Obama was on the ballot, state House Minority Leader Stacey Abrams noted that the Obama campaign did not expend significant resources in Georgia and said there was a lingering perception in the state that he wouldn’t win anyway.

“People who didn’t register to vote for President Obama in 2012 or 2008, they did not have someone coming to their door saying we have a chance to win,” Abrams said. “With Michelle’s race, there will be a concerted effort to register and mobilize and turn out voters.”

Beyond winning over some moderate Republicans and getting potential Democratic voters registered and to the polls, the midsummer GOP primary runoff will mark a turning point in the race to replace retiring Sen. Saxby Chambliss. At a recent 90-minute Republican debate in Augusta, Nunn’s name wasn’t uttered until the final three minutes — anecdotal of the reality that Nunn has so far gone largely untouched.

National and state Republicans remain skeptical that she can put together a winning coalition of voters, but there is concern that the GOP nominee who emerges from the July 22 runoff will turn out to be someone Democrats can effectively label as far outside of the mainstream.

“It won’t take more than a few ads pointing out Nunn’s first vote will be for Harry Reid for majority leader — and that enables the entire Obama agenda — to end any serious flirtation moderate, suburban white voters will have with her,” said Joel McElhannon, a veteran Georgia Republican consultant. “The only real risk Republicans have of losing is if we nominate someone perceived as too extreme to those voters — so extreme it trumps concerns about Obama’s agenda.”

The two candidates most often mentioned by Republicans as concerning are Reps. Paul Broun and Phil Gingrey, conservatives with track records of controversial comments.

The front-runners in the May 20 GOP primary are former Reebok and Dollar General CEO David Perdue, the cousin of former Gov. Sonny Perdue, who is running as the outsider in the race, and Rep. Jack Kingston, who touts both his conservative record and his willingness to make his party’s case on MSNBC and HBO’s “Real Time with Bill Maher.”

Either would likely make winning in November a taller climb for Nunn.

Former Georgia Secretary of State Karen Handel, who was nearly nominated for governor in 2010, has struggled to keep up financially with Perdue and Kingston but is hoping for a late surge to make the runoff.

Another Georgia Republican insider was far more concerned about the possibility of a Nunn victory but noted her campaign’s challenging weave of messaging to attract both moderates and fervent supporters of the president.

“She’s raising money and doing a good job of distancing herself from the White House without alienating her base,” the Republican said. “If she wins, it’s going to be by a razor-thin margin, but it’s possible.”

One path for Democrats outlined in an analysis of demographic and voting data by the Atlas Project, a Democrat-aligned firm, includes improving performance in metro Atlanta and at least matching former Senate nominee Jim Martin, who took Chambliss to a runoff in 2008, everywhere else. It also notes Democrats must take more than 50 percent on Election Day to avoid a runoff, which this cycle would be held on Jan. 6.

In Columbus, Nunn was on the second of a three-day tour highlighting the local benefits of public-private partnerships. Here, she spoke with the owner of a newly opened whitewater rafting company, WhiteWater Express. It was drawn to the area by a new man-made rapids course — “the longest urban whitewater rafting in the world,” according to the company — which was enabled by the commitment of both government and private resources to rejuvenate the river and downtown.

Cardin had heard about Nunn from her daughter and wanted to see the candidate for herself.

“I’m drawn to her as a candidate, and I just think we need more people like her in Washington rather than some of the people that are there,” Cardin said.

That afternoon, Richard Spencer, a 48-year-old garden designer from Albany, who also voted for Romney, came to a home in nearby Shellman to meet the daughter of one of his heroes. He’s hoping she can influence Democratic leadership in Washington.

“The feeling I’m getting from Michelle is just like Sam, and I love that,” Spencer said. “Give me someone who can infiltrate that side with some common sense.”

The Georgia Senate race is rated Favored Republican by the Rothenberg Political Report/Roll Call.

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A Low-Key Paul Broun Campaigns for Senate in Georgia

First Karen Handel TV Ad Features Sarah Palin

Westmoreland: Perdue ‘High School Graduate’ Comments ‘Stupid’

Jack Kingston Raised $1.1 Million in 1st Quarter

Gingrey Vows to Repeal Obamacare in First Term or ‘Go Home’

Photos From Roll Call on the Road