It is a suitably dramatic ending to the 2020 election cycle. When voters in the Southern US state of Georgia go to the polls on January 6th to vote for two senators, they will also decide much more.

If Democrats can win both races, President-elect Joe Biden will have a working Senate majority, albeit a razor-thin one. Lose just one race, and the new administration will have to contend with a divided Congress. Republicans, under their Majority Leader Mitch McConnell, will block much of the president’s agenda from day one.

The runoff races – triggered by a first-round failure to win a majority – see Republican incumbents David Perdue and Kelly Loeffler go up against Democrats Jon Ossoff and Raphael Warnock. Perdue, formerly senior vice president of sports brand Reebok, has been a senator since 2014. He fell just short of a majority in the first round against Ossoff.

Businesswoman Loeffler, meanwhile, was chosen by Governor Brian Kemp for a Senate seat left vacant by the retiring Johnny Isaakson. She came second in a special election on November 3rd, in which numerous Republican and Democratic candidates all competed against each other. In first place was Warnock, an African American who is senior pastor of the famed Ebenezer Baptist Church in Atlanta, a job once held by Martin Luther King.

The elections come at a time of soul-searching within the national Republican coalition, which has made a particular impact in Georgia. Outgoing President Donald Trump has soured on Governor Kemp and Georgia Secretary of State Brad Raffensberger, following his shock loss in Georgia. Trump, the first GOP loser in the state since the Clinton era, went so far as to call for the two to be jailed because they did not support Trump’s claims about election rigging.

Some Republicans are worried that these bitter fault lines risk hurting the party’s candidates in the Senate contests. Many Georgian conservatives, believing the results of the presidential election were fraudulent, will sit this one out. Most recently, Frank Luntz, an influential Republican pollster, voiced fears about the electoral effects of the president’s conduct on Fox News.

The Republican candidates have been pursuing a relentlessly negative campaign, seeking to wrongly tar their opponents as radical leftists. In the case of Warnock, attacks from Loeffler have attracted accusations of racism from and against African American Christians. “We see your attacks against Warnock as a broader attack against the Black Church and faith traditions for which we stand,” wrote more than 100 faith leaders from multiple states in an open letter.

By contrast, the Democratic campaign has championed reform and aid for the state and country in the wake of Covid-19, with the slogan “Health. Jobs. Justice.” Warnock and Ossoff have campaigned together since their first rounds.

Their proudly progressive campaign marks a change from the established Democratic strategy in Southern

states of fielding white, Christian conservative Democrats in the hope of peeling away some white Republican votes. Ossoff, though white, is Jewish American. The shift in strategy and tone reflects an increased confidence following Biden’s win here, and the lasting impact of black voting rights activist Stacey Abrams’ impressive showing in the 2018 Governor race.

The polls show a nail-bitingly close contest, with less than a percentage point  between candidates in both races. President-elect Biden’s visit to the state in mid-December highlighted the national importance of the election. In a deeply partisan Washington, there is little hope of passing much through Congress without controlling both the House and Senate.

Key issues on the agenda, like climate change and affordable healthcare for Americans, will be more difficult for the president to address without a Democratic Senate. The frustrations of dealing with a right-leaning Senate would also pose problems for Biden, as the left fringe of the Democrats, strengthened by the presidential election results, demands an increasingly progressive agenda.

The pivotal nature of the election has attracted a steady flow of donor money for both sides. In particular, the involvement of Wall Street dollars has underlined the financial lobby’s continued importance in US politics. Top Republican donors include Stephen Schwarzman of Blackstone Group, while the pro-Democrat Super Majority Pac also received $10.2m from Renaissance Technologies. Nonetheless, Republicans have had a clear edge in fundraising, putting pressure on the Democratic campaign.

Whatever the result, the ramifications of these elections will be even greater than the interest they have generated. In a country and state yet to recover from the splits of November’s election, expect the vitriol and mudslinging to continue long after the dust has settled.