Progressives poured $23 million into Jon Ossoff's campaign. House Democrats' campaign arm sent a team to Georgia to organize the sixth congressional district months ahead of the special election there.
Now, voters will decide whether all the effort was worthwhile.
Ossoff and Republican Karen Handel are facing off Tuesday in what has become the most expensive House race in history, with the candidates, their parties and super PACs pouring more than $50 million combined into the effort to win a single House seat in the northern Atlanta suburbs.
More than 140,000 voters cast their ballots early -- an astounding number for a special election, and one that nearly matches presidential contests.
The race is being viewed nationally as a gauge of whether President Donald Trump's sagging approval ratings are a drag on Republicans that could threaten the party's control of the House in the 2018 midterm elections.
Democrats, meanwhile, see in Georgia an early test of their strategy of trying to win typically Republican seats in suburban areas -- districts that are relatively highly educated, wealthy and diverse.
Trump weighed in on Twitter late Monday and early Tuesday, attacking Ossoff for living just outside the district, claiming Ossoff will raise taxes and calling Handel a hard worker "who will never give up!"
With the inflated price tag and the 15-month lag time between the special election and the November 2018 midterms, the contest might not hold much predictive value.
But it could be a huge psychic boost for the winner's party -- and a blow for the loser's.
If Ossoff were to win, Democrats would have a clear victory that could help keep the party's hyper-engaged base -- and donor community -- energized. A loss, though, would be a major disappointment.
If Handel were to win, Republicans on Capitol Hill could feel they are on the right track -- helping the GOP's push for health care and tax reform legislation. It could also show House incumbents that they can separate themselves from Trump effectively on the campaign trail, and stave off a potential wave of retirements.
Ossoff and Handel were the top two finishers in an April 19 primary, advancing to the one-on-one runoff election.
The district has historically leaned heavily Republican. Former Rep. Tom Price, whose departure to become Trump's health and human services secretary led to the special election, won each time he was on the ballot since 2004 with more than 60% of the vote. Mitt Romney carried the district by more than 23 points when he faced former President Barack Obama in 2012.
However, it was Trump's collapse -- besting Hillary Clinton by just 1.5 points in the district in 2016 -- that led Democrats to believe it could be in play.
It's the best shot the party has of the four House special elections this spring to win a seat that now belongs to Republicans. But in November 2018, Democrats are expected to have many better pick-up opportunities. According to the Cook Political Report's Partisan Voter Index, there are 71 Republican-held districts that have less GOP-leaning electorates than Georgia's sixth district.
Polls close in Cobb, Fulton and DeKalb counties -- the three that include part of the district -- at 7 p.m. ET.