This is the most expensive House race in history (more than $50 million has been spent) and the most eagerly awaited special election this year.
The Georgia 6th is an affluent and well-educated district that has elected Newt Gingrich, the former speaker; Johnny Isakson, now Georgia's senior US senator; and most recently Tom Price, who resigned in February to join the administration.
The most expensive House race in US history ends with the voting Tuesday night in a special election in North Atlanta billed as a referendum on Donald Trump's presidency. Recent polls have the two neck and neck.
Mr Ossoff narrowly failed to win the 50% needed to secure outright victory in the election for the Atlanta seat in April, forcing this run-off vote against Ms Handel. With questions swirling around ongoing investigations into whether the Trump campaign colluded with Russian Federation and the lack of major legislative accomplishments, many pundits believe an Ossoff win could panic Republicans into thinking their current approach isn't working.
Republicans are facing a sobering reminder of their president's poor approval ratings, as 30-year-old centrist Democrat Jon Ossoff, a filmmaker and onetime political assistant, clings to the narrowest of leads.
Republican candidate Karen Handel, shown campaigning in Alpharetta, Georgia, on June 19, is a former secretary of state of Georgia.
But as Democrats angle for an upset, Republicans in Georgia and across the country have fallen in line around their own candidate, Karen Handel.
The question is whether these scores of what have historically been reliably GOP voters are separating this race from their distaste for Trump and sticking with Handel - or have been turned off more broadly by the Republican brand under Trump and are willing to back Ossoff. All that attention has drawn nearly $60 million of spending from both sides - a record for a House race - into the suburban Atlanta district. The scramble to replace him has been entirely influenced by the unpopularity of the new president-despite the fact that Price has never collected less than 60% of the vote in 14 years of elections, the Democratic candidate has a chance to flip the district.
Many have their eye on reclaiming a Democratic majority in the House in 2018. Making his first bid for office, he has become a symbol of the Trump opposition movement.
The stakes are highest for Republicans, who have held the district since the Carter administration without much of a challenge to speak of.
For much of his campaign the young Democrat newcomer Jon Ossoff sought to harness local dissatisfaction with President Donald Trump, who carried this affluent, suburban district by only 1 percentage point in last year's presidential election.
Handel touts her experience in the private sector and has an agenda similar to Trump's. "We want people around the country to focus in and say: This is an opportunity for us to push back and hold MacArthur accountable for his actions". The polls in Cobb, Fulton and DeKalb counties - the three where the sixth district House seat is located - close at 7 p.m. ET on Tuesday.
If he wants to pull off a victory in a traditionally red seat, he'll need to drive up those numbers.
The outcome of Georgia's contest is likely to become a prism through which congressional Republicans view Trump - a reality with major policy and political implications. There's another contest in South Carolina Tuesday in which the Republican candidate is favored.
"It's not just symbolic - we really can't afford to lose any seats at this point", said Rep. Tom Rooney, R-Fla., noting that "the factions" among congressional Republicans make their majorities more tenuous in practice than they may seem on paper.
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.
Ossoff raised more than $23 million, most from outside Georgia.
The latest Real Clear Politics poll average shows Ossoff narrowly ahead of Handel with 49.3% to her 47.8%.