Ossoff has raised a record US$8.3 million, albeit much of from national donors, and received support from big names in the party such as Nancy Pelosi.
He has also mobilised a diverse mix of thousands of grassroots supporters, who are bussed in from around the country, and is fighting an effective ground game - something Clinton tellingly failed to do.
The Georgian is carrying the hopes of many within the Democratic Party, perhaps unfairly at this early stage of his political career, but the burden does not seem to weigh heavy.
"The national and international interest [in the campaign] is just background noise compared to the intensity and passion of the volunteers - thousands of them, many of whom have not been engaged with politics before but who are standing up right now," Ossoff told the Daily Telegraph.
"There are many in the community who are concerned by the direction of things in Washington and have serious concerns with respect to the Administration - and I share many of those concerns."
One supporter, David Yu, a former banker and Reagan voter, said he had been terrified by the way the Trump Administration has started out.
"I feel the fear. I feel it for me, for my children and for my grandchildren. The racial hatred is frightening," he said.
The election was triggered by Trump selecting Tom Price, the incumbent Republican congressman in the district, to be his Health Secretary.
The seat, held by former House Speaker Newt Gingrich for 10 straight terms, is a Republican stronghold. There has not been a Democrat victory here since 1974.
Ossoff, a documentary filmmaker and former congressional aide, who studied for a masters degree at the London School of Economics, appeared to be relishing the challenge.
While at high school, he interned for John Lewis, the Democratic Georgia congressman whose civil rights heroics Trump appeared to be unaware of when he attacked him on Twitter in early January.
It was Lewis who persuaded Ossoff that he could win Georgia's sixth and polls now have him as high as 43 per cent in a crowded field. The Republican contenders, split between pro-Trump and establishment supporters, are also no doubt helping the Democrat at this stage.
If he secures more than 50 per cent of the vote tomorrow, he wins outright. Otherwise he will face a run-off in June, by which time the Republicans are expected to have coalesced around a single candidate.
Aides said as much as 20 per cent of the Ossoff support is from Republicans dismayed by Trump.
"The coalition the campaign is building includes many Republicans and independents... I'm going to work across the isle to get things done," Ossoff stated, striking a non-partisan tone.
In 2009, Republican Scott Brown's special election victory in Ted Kennedy's Massachusetts seat foreshadowed a rout of the Democrats at the midterms the following year.
The Republicans are clearly concerned about Ossoff doing something similar for the opposition.
"We've held this seat for 37 years, and we're planning on keeping it for another 37," said Maddie Anderson of the National Republican Congressional Committee.
A Republican fundraising committee has poured millions into attack ads targeting Ossoff's age and inexperience.
His rivals have also made unsubstantiated claims that he has been putting up yard signs in people's gardens without permission.
Such tactics are "scraping the bottom of the barrel," Ossoff said. "It's predictable, cynical smear politics with a whiff of desperation."
Whatever happens in Atlanta, it remains a difficult path back to power for the Democrats. But if Ossoff pulls off a win, it will be a ray of hope for his party.
