The race to represent the 7th District, which includes portions of Gwinnett and Forsyth County, was the closest congressional contest in the country last year. Once lily white and deeply conservative, the district is now at the center of the demographic shifts that have transformed Atlanta’s wealthy suburbs into political battlegrounds.

The 7th District contest only received a fraction of the attention as the neighboring 6th District last year -- most outside money went there or to the governor’s race -- but that’s widely expected to change over the next 21 months.

The Democratic Congressional Campaign Committee has already short-listed the 7th District as a prime pickup opportunity for 2020, and Democratic Party of Georgia Chairwoman Nikema Williams said the district is a “microcosm of the new Georgia as a whole.”

“Rob Woodall is calling it quits because he sees the writing on the wall, and he sees the same Georgia that we do: One that is growing, more diverse, and more progressive,” said Williams, also a state senator.

In addition to Bourdeaux, several other Democrats are said to be eyeing the seat, including state Reps. Sam Park and Brenda Lopez. Snellville attorney Marqus Cole has already announced his candidacy.

A bevy of Republicans are also now eyeing the seat. Potential candidates include U.S. Attorney B.J. Pak, a former Gwinnett state legislator; state Sen. Renee Unterman; ex-state Rep. Scott Hilton and former state Sen. David Shafer. Ex. state Rep. Buzz Brockway, who ran unsuccessfully for secretary of state last year, is also looking at the race, as are state Sen. P.K. Martin, former Woodall challenger Shane Hazel and Mike Royal, a state school board member and former Gwinnett GOP chair.

Health care was at the heart of Bourdeaux's campaign in 2018, and she said it will be a central theme in her second bid for Congress, in addition to privacy issues, voting rights and overhauling the campaign finance system.

Read more: Bourdeaux says commitment to public service drives run for Congress

Bourdeaux enters the 7th District Democratic race with a significant leg up over many potential challengers. Her campaign committee ended last year with nearly $142,000 in the bank, and she built a formidable fundraising network during her last campaign.

She said she chose to announce her candidacy early because she wanted “more runway” to fortify relationships with grassroots organizations in the district.

"The last race was so fast and so intense,” she said, adding that she wanted time to “have coffees, have town halls, talk about some key issues with people. There's just so much more that can be done."

Republicans were swift to denounce Bourdeaux’s return.

“Carolyn Bourdeaux couldn’t ‘finish the job’ the first time and it won’t be any different the second time around as voters continue to reject a socialist Democratic agenda that’s becoming more and more extreme with each passing day,” said Camille Gallo, a spokeswoman for the National Republican Congressional Committee.

Staff writer Greg Bluestein contributed to this article.

Read more: U.S. Rep. Rob Woodall will not seek re-election