As the calendar turns to a blockbuster election year, Georgia’s U.S. Senate hopefuls are spending the final days of 2013 seeking enough campaign cash to make a statement about their viability, a task that becomes more difficult once easy funding sources are exhausted.

An Atlanta Journal-Constitution analysis of campaign finance disclosures shows how the chief contenders have carved out different fundraising niches and underscores the challenge they confront in 2014 in a crowded race that’s expected to cost more than $10 million.

As the end-of-year financing deadline looms, the candidates face added pressure to show they are either tapping deeper into those bases or broadening their appeal to new supporters. The tallies take on added importance this year with the earliest primary in Georgia’s recorded history set for May 20.

Among Republicans, former Georgia Secretary of State Karen Handel is mining her north Fulton home base, U.S. Rep. Paul Broun is cultivating conservatives across the country through direct-mail solicitation and U.S. Rep. Phil Gingrey is hitting up fellow physicians.

U.S. Rep. Jack Kingston has been the most prolific so far by leaning on his neighbors in South Georgia, while former Fortune 500 executive David Perdue is relying partly on allies of his cousin, former Gov. Sonny Perdue, to prove his campaign’s mettle — as well as more than $1 million so far from his own personal wealth.

Democrat Michelle Nunn, meanwhile, has attracted backing from Washington Democrats, outside groups and her own networks in the nonprofit world, not to mention friends of her father, former U.S. Sen. Sam Nunn.

The large field has assembled to replace retiring Republican U.S. Sen. Saxby Chambliss in a race that’s drawing national attention for its wide-open GOP primary and for the outside chance Democrats could break their statewide losing streak. Year-end fundraising tallies will be released at the end of January and, particularly in the GOP race, used as a measuring stick for the final push to the primary.

“Just as much as resources, the reports that come out, it’s about meeting or beating expectations,” said Chip Lake, a Republican consultant and former adviser to Gingrey. “Jack Kingston has proven to be a very strong fundraiser, and so one of the questions that everybody has is: Will that slow down for Jack or will he continue to show the same strength from donors that he’s shown the first three quarters of the year?”

Kingston, who emerged as a fundraising front-runner with $1.29 million in individual contributions from May through September and an additional $145,000 from political action committees, has turned to his neighbors for help. Donors from a handful of ZIP codes around his Savannah home already have tossed in more than $250,000 toward his Senate bid, and they expect the campaign to hit them up for more.

One is Pat Hackney, a retired University of Georgia employee who has known Kingston since before he entered the House.

“I remember the day I was out working in my garden and Jack came by — on foot — asking for people to vote for his House race,” she said. “He’s very approachable.”

While political action committees are the lifeblood of Washington incumbents, so far they haven’t had an outsized impact in the contest.

Gingrey got a surge of PAC money just before he announced his Senate bid — $223,000 in March alone — but the money slowed to a trickle after that. The American College of Radiology PAC sent a $2,500 check the same day Gingrey announced for the Senate, though the PAC is remaining neutral in the race.

Ted Burnes, the director of the radiologists’ PAC, said Gingrey and his congressional rivals have not been hitting the Washington PAC circuit hard, particularly compared with candidates in other marquee Senate races.

“This Georgia one is really, really quiet,” Burnes said. “And I don’t know if it’s just because of so many incumbents running and people are scared to get in. … There hasn’t been real outreach for raising money that I’ve heard at all on the Republican side in this race. It’s very bizarre to me.”

Broun, an archconservative with a national profile, has largely relied on donations from fellow physicians, out-of-state Republicans and tea party types who agree with his message. His support likely was boosted by an early endorsement from former U.S. Rep. Ron Paul of Texas, who has a fervent national following after libertarian-leaning campaigns for the presidency.

Broun's list of out-of-state donors, which makes up nearly two-thirds of his contributions, includes big names such as billionaire George Lindemann, radio host Peter Schiff and author Dean Koontz. They also include rank-and-file conservatives, including Harry Brandt, who worked in the financial industry in Chicago before retiring recently to Florida.

“He represents the conservative values that are so important to support in this country. The country is turning more liberal all the time, and I think Congressman Broun will be a great senator,” said Brandt, who has donated at least $2,600 to Broun’s campaign after hearing him speak at several forums. “He seems like the kind of guy who, if he were in Florida, I would support.”

Nunn is attracting donors from far and wide for other reasons. When she joined the race in July, leading Democrats in Washington and Georgia immediately anointed her as their pick — much to the consternation of the other Democrats in the race, who have raised comparatively paltry sums.

Nunn brought in $1.7 million in her first two-plus months as a candidate, with more than a third coming from outside Georgia. Emily’s List, a Washington-based group dedicated to electing Democratic women who support abortion rights, bundled $30,000 in donations to Nunn in about a month.

Nunn has spent more than two decades in the nonprofit world, ascending to become CEO of the Points Of Light, a volunteer service organization with an international profile.

Among her donors is Bob Cunha, who got to know Nunn when they both served on the board of Hands On Atlanta. Cunha, who lives in the Boston area, rarely donates to political candidates, but he liked what he saw in Nunn.

“There are people all over the country who have been touched by Michelle’s work and have worked with Michelle in the nonprofit sphere,” said Cunha, who gave the maximum $5,200, split between the primary and general elections. “Fundraising in politics is not my world, but Michelle is a close friend and she’s someone who I think would do tremendous work in the United States Senate.”

By contrast, Handel’s haul has come almost entirely from within the state of Georgia. The former Georgia secretary of state emphasizes the fact that she does not have the D.C. connections of the three congressmen, and she maintained her ties across the state from a near-miss run for governor in 2010.

Sidney Brown, an attorney at Jones Day in Atlanta, has supported Handel since she was on the Fulton County Commission.

“People haven’t forgotten her,” Brown said. “And she’s serious. She’s intelligent. She knows the issues. I don’t think she’s running just to be in office.”

Perhaps Handel’s chief shortcoming as a candidate is her fundraising. Her $440,000 in donations for the year trails all the top-tier candidates, though she kept pace with Broun and Gingrey in the third quarter. An improved showing in January could go a long way toward elbowing out her rivals.

“She needs to pick up some more endorsements and raise some more funds,” Brown said. “Some of these other candidates are sort of weak, and I don’t see them hanging in for the long haul.”

David Perdue drew on many of his cousin’s supporters for staff and contributors. Josh Belinfante is both.

Sonny Perdue’s former executive counsel is now an attorney for David Perdue’s campaign and donated to the cause as well. Belinfante said he has known David Perdue for years before he entered politics, and his practical, business-minded perspective makes him an attractive first-time candidate.

Belinfante said the Perdue family network and David Perdue’s business connections have proved fruitful in the early going, in addition to the candidate putting $1.1 million of his own money into the race.

“Yes, he’s contributed and loaned good sums of money to his campaign, but he’s also out raising money from others and continuing to do so,” Belinfante said. “It’s always nice to work with a candidate that can put in the kind of money he has, but it’s not a substitute for his message.”