Stacey Abrams’ decision to pass on a campaign for U.S. Senate will quickly heat up a race that was essentially frozen for months as she struggled over whether to challenge first-term Republican U.S. Sen. David Perdue.

The sidestep was a blow to national Democrats who saw Abrams as their best chance to flip a seat that has been in Republican control for nearly two decades. It also leaves the party without an obvious front-runner who could clear the field and avoid a divisive primary.

Former Columbus Mayor Teresa Tomlinson tried to show she was off to a fast start Wednesday when she formally launched her campaign with a video highlighting her two terms as the west Georgia city’s leader.

“It’s time to bring the same smart, pragmatic, effective government to Washington, D.C., without all the crazy and the mean,” she said, criticizing Republican immigration stances, protectionist trade policies and opposition to Medicaid expansion.

Tomlinson is likely to get some company. Sarah Riggs Amico, the runner-up for lieutenant governor in November, is considered likely to run, and former 6th Congressional District candidate Jon Ossoff is a possible contender. A handful of other Democrats could enter the race.

Read more: Who could challenge Sen. David Perdue in 2020

“Part of it is to finish what we started last year,” Amico said of her 2018 campaign for statewide office on the same ballot as Abrams. “We energized a lot of communities and voters who found a touch of hope for the first time in a while. We gave them something to vote for – not vote against.”

It will be hard for the lesser-known candidates to match the name recognition or grassroots field apparatus that Abrams had at the ready, or a fundraising operation that comes close to rivaling Perdue’s machine.

Tomlinson, however, has had a jump-start thanks to paperwork she filed in early April that allowed her to start raising cash but came with the caveat that she would only compete if Abrams did not. That's allowed Tomlinson to raise roughly $300,000 and hire veteran operatives to run her campaign.

Among them is ex-Abrams finance director Edana Walker and the political firm that helped engineer Democrat Doug Jones’ upset Senate victory in Alabama. She expects to soon name well-known Georgia strategist Kendra Cotton as her campaign manager.

For Ossoff, who has held a string of recent town halls to gauge his appeal, a Senate campaign would present a different sort of challenge.

He raised $30 million and marshaled thousands of volunteers during his unsuccessful 6th District campaign in 2017, a special election seen as a referendum on President Donald Trump. A Senate run would test his ability to expand that network statewide.

Though the race is about 18 months away, the time crunch has already begun. The Democrats will have to race to define themselves before Perdue can do it for them. And they’ll have to contend with an opponent with solid approval ratings.

recent Atlanta Journal-Constitution poll showed about 47% of Georgia voters rated Perdue favorably, though he struggled in metro Atlanta. Across the state, only one-quarter of voters view him unfavorably, and about the same proportion don't have an opinion.

Former Columbus Mayor Teresa Tomlinson/AJC file

icon to expand image

Before they can focus on Perdue, though, Democrats will have to hash out what could be a contentious party battle for the nomination - something they have mostly avoided in recent contests.

AJC Interview: Abrams reveals why she won't run for Senate

In 2014, Jason Carter and Michelle Nunn had little or no opposition during their bids for governor and the Senate, respectively. And in 2016, Jim Barksdale was the only candidate with support from party leaders to jump into the race against U.S. Sen. Johnny Isakson.

The 2018 race may have been a sign of things to come, as Abrams squared off against former state Rep. Stacey Evans in a bitterly fought primary. Abrams’ overwhelming victory, though, meant she had already unified her party.

Democratic officials say whoever emerges from next year’s primary will enjoy the party’s support.

“Stacey Abrams would have been a great senator, and so will the candidate who takes on Senator Perdue next fall," said Stewart Boss, a spokesman for the Democratic Senatorial Campaign Committee.

‘Stark contrast’

Republicans, of course, are rooting for the messiest of nominating contests across the aisle.

And GOP groups quickly framed Abrams’ decision as a disastrous failure by U.S. Senate Minority Leader Chuck Schumer that leaves Democrats "stuck with an assortment of second-tier candidates” and a “JV-team primary” to challenge Perdue.

The former Fortune 500 chief executive, too, is readying for the new phase of his campaign.

With the support of the White House and little threat of a credible primary challenger, Perdue has restocked his campaign account, built up his political operation and sharpened poll-tested messages aimed at "socialist" Democrats or asserting unflinching support for Trump.

President Trump, center, with U.S. Sen. Tom Cotton, left, and U.S. Sen. David Perdue of Georgia. (AP)

icon to expand image

"We're going to run against somebody from the Democratic side that's going to be well-funded, and they're going to espouse this radical social agenda that (Democrats are) trying to perpetrate right now, so I'm geared up," Perdue told reporters Tuesday. "We're going to be ready."

Perdue amassed a formidable $1.8 million during the first three months of the year. He also paid a $30,000 fine to the Federal Election Commission, settling an inquiry into his bookkeeping from the 2014 campaign.

He’s quietly rearranged his staff to prepare for his re-election fight, shifting longtime top aide Derrick Dickey and several other members of his congressional team to his campaign. And he’s toured extensively across the state for both official and campaign-related events.

Perdue has mostly ducked chances to criticize Abrams or other potential Senate hopefuls, but his recent appearances previewed the messaging that will dominate his campaign.

Read more: Inside David Perdue's 2020 race for another U.S. Senate term

He emphasizes his close ties with Trump and credits Republicans with fostering a solid economic climate. He trumpets the federal money he helped secure to deepen the Savannah harbor. And he paints Democrats as “extremists” out of touch with the nation’s political norm.

"Once Americans see the stark contrast between what we Republicans are offering and the liberals, they'll stand up and go to the polls," Perdue said at a recent tea party gathering, lacing his speech with warnings that Democrats will try to seize permanent control of Congress should they flip the Republican-controlled Senate.

“It’s up to us to make sure we don’t sit back, like some of us did in 2012, and let it happen,” he said.

Attack lines

Then-Gubernatorial candidate Stacey Abrams links hands with Lt. Governor candidate Sarah Riggs Amico during the Georgia Democrat convention in 2018.

icon to expand image

Though some state and national Democrats are disappointed in Abrams' decision - Schumer, for one, relentlessly recruited her to run - the party must now hone a new strategy to flip Georgia.

Zell Miller was the last Democrat elected to the Senate in 2000, and four years later he headlined the Republican National Convention. No Democrat has won statewide office in Georgia since 2006.

But Democrats are hoping to channel the suburban anti-Trump rage that booted more than a dozen Republicans from the state Legislature and nearly delivered Abrams to the Governor's Mansion last fall.

And beyond an embrace of more liberal issues that Georgia Democrats once avoided, such as gun control, one line of attack they’re sure to engage is the stalemate of a $14 billion Hurricane Michael relief bill that’s stalled in Congress despite Perdue’s outspoken support.

The package, which would include $3 billion in relief to farmers, is sidelined despite outspoken support by Perdue and other GOP leaders amid partisan feuding over funding for Puerto Rico.

The Republican and his allies say Democrats are playing politics to deny Trump a political victory, but Tomlinson and other Georgia Democrats have blamed Perdue for refusing to stand up to the president.

Democrats are also sharpening critiques of Perdue for his support of legislation adding to the national deficit – he's long warned the growing debt is a crisis – as well as recent gaffes that include snatching a Georgia Tech student's cellphone at a tailgate last fall.

And while Abrams indicated she will stay neutral in the nominating contest, she’ll use her platform to pummel Perdue early and often.

“Let’s be clear,” she said, “I will do everything in my power to ensure Georgia elects a Democrat to the United States Senate in 2020.”

Stay on top of what's happening in Georgia government and politics at www.ajc.com/politics.