Voters in Georgia head to the polls Tuesday to decide what has become the most expensive House race in history.

Democrat Jon Ossoff and Republican Karen Handel have together spent more than $50 million in their race to fill the seat left vacant by Health and Human Services Secretary Tom Price.

It’s just the latest special election since Trump was elected to garner outsized attention in the Trump era.

For Democrats, a win in Georgia’s 6th Congressional District would mark a substantial win. Once held by former Speaker of the House Newt Gingrich, the solidly Republican seat was last held by a Democrat in 1979. For Republicans, avoiding an embarrassing defeat would give them a sense of relief as Congress charts a path amid Trump’s constant controversies.

Heading into the final day of the pivotal race, here are five things you need to know.

Who is Jon Ossoff?

The 30-year-old candidate is former documentary filmmaker who once served as national security aide for Democratic Georgia Congressman Hank Johnson. He considers Rep. John Lewis, for whom he interned in high school, a mentor.

He’s been labeled an “outsider” by his opponent, a carpetbagger who is different from the Georgians he’s hoping to represent, despite having been born in the district. He lives just outside of the district with his fiance who is in medical school at Emory University—their place of residence has kept Ossoff from being able to vote for himself.

Despite behind heralded as somewhat of a Democratic savior in the wake of the party’s embarrassing 2016 loss, Ossoff is not a liberal’s dream. He rarely mentions Donald Trump, won’t mention impeachment and likes to note how “tired” voters are of partisan rhetoric. Ossoff has recently sounded more centrist themes, coming out against single-payer health care and higher taxes.

Regardless, left-leaning politians from Rep. John Lewis to Sen. Bernie Sanders have expressed support for the candidate and he appears poised to maintain the support of the district’s Democrats.

Who is Karen Handel?

Former Georgia Secretary of State Karen Handel has a lot of experience. She served as the state’s Secretary of State from 2007 until 2010 and has run for office, unsuccessfully, twice— for governor against Nathan Deal in 2010 and for the Senate seat now held by Sen. David Purdue in 2014. As Secretary of State, Handel supported strict voter ID laws and defended a controversial voter roll purge in the state.

Handel also served as the senior vice president of public policy at the Susan G. Koman Foundation from 2011 to 2012, but left shortly after a nasty, public battle between the charity organization and Planned Parenthood over a canceled and later restored grant. Handel detailed her experience in a book titled Planned Bullyhood, in which she denied that the decision to initially cut the funds to the Planned Parenthood had anything to do with abortion.

Handel has at times appeared reluctant to appear too close to President Trump in the race, telling Fox News her job is “isn’t to be an extension of the White House” in a late April interview though she has made clear she supports him. President Trump urged voters to support Handel in a tweet on Monday morning, ahead of the runoff.

The race so far

Back in April, when the first votes were cast in the special election, Ossoff just missed winning the seat outright: he garnered 48.1% of the vote, just a few points shy of the 50% he needed to win.

Some 140,000 early votes have already been cast in the runoff, but the outcome of the race is hard to predict. Handel and Ossoff are nearly deadlocked according to the latest polling; a RealClearPolitics average has Ossoff with a narrow edge with 49.6% of the vote compared to Handel’s 47%.

Given the seat’s Republican history and the GOP’s success in special elections thus far, it would be easy to write the race off another that will result in a near-win for the left. But Democrats, still reeling from Clinton’s historic loss, are hoping their voters are energized enough by anger and calls for resistance to head to the polls in droves.

In recent weeks, the race has gotten increasingly contentious, with an outside ad linking the shooting of Rep. Steve Scalise in Virginia to Ossoff and Handel’s stance on same-sex adoption being called into question.

History of the seat

In November, it was clear that some conservatives in the district voted for former Secretary of State Hillary Clinton. Trump won by just 1.5% points in November, according to the Atlanta Journal-Constitution. Analysts have said education was a major factor in Trump’s narrow win in the area, which includes the affluent suburbs of Atlanta, where 60% of voters are college educated and therefore more likely to favor Clinton.

But in 2016 a vote for Clinton did not mean a vote for Democrats down ballot as then-Rep. Tom Price won his reelection by 24 points—the same point difference 2012 presidential candidate Mitt Romney had over former President Obama.

The Journal-Constitution notes that a Democratic Congressional candidates have not won more than 40% of the vote in the district in 21 years.

The race’s impact

The widespread attention the race has garnered has translated into loads of cash: some $50 million have been spent in the race making it the most expensive House race in the nation’s history. If the seat shifts from Republican to Democrat, it’ll be the first special election lost for the GOP in 2017: races in Montana and Kansas have already gone their way and a race in South Carolina is expected to result in a Republican win.

But, beyond shifting the seat, the results of Tuesday’s special election could also be a critical factor in the future of the Republican agenda. Democrats are hopeful that a win in what had been such a solidly Republican district could throw the GOP off balance ahead of the pivotal midterm elections. Democrats need a total of 24 seats to take back the majority in the House, and win in Georgia would bring them a step closer.

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