Joe Biden is leading the US presidential race as a handful of states continue to count ballots, but the picture is much less rosy for Democrats in Congress. Although Democrats had anticipated a blue wave on election night to gain control of the Senate, they may not eke out even a slim majority. The future balance of power in the Senate will come down to a razor-thin margin and hinges on the results of the four remaining races – one in Alaska, another in North Carolina and two in Georgia. “I don’t know if I’m going to be the defensive co-ordinator or the offensive co-ordinator,” Senate Majority Leader Mitch McConnell said on Wednesday. In Alaska, the Republican incumbent Dan Sullivan still holds a firm lead over his challenger, Al Gross as the state continues to count ballots. North Carolina, a key battleground state, also continues to count a number of remaining ballots that will determine whether Republican Thom Tillis will keep his Senate seat. Mr Tillis has already declared victory in the competitive race against Democrat Cal Cunningham even though the ballot count is not yet complete. In the final weeks of the race, Mr Cunningham had come under attack for reports of a second extramarital affair. If Mr Sullivan and Mr Tillis hold on to their seats, Republicans will need to win at least one of the two races in Georgia to maintain their majority if Mr Biden wins the White House since his running mate Kamala Harris would serve as the tiebreaking vote in a split Senate. Under Georgia’s unique election law, a Senate race goes to a run-off in January if no candidate gains more than 50 per cent of the vote. The Republican incumbent David Perdue is teetering on the 50 per cent threshold. However, it remains unclear whether he can avoid a runoff against Democrat Jon Ossoff as the state continues to count its ballots. In Georgia’s other race, the incumbent Kelly Loeffler was also unable to pass the 50 per cent threshold because another Republican running to her right has split the conservative vote. She is expected to move into a run-off election with Democrat Raphael Warnock, raising the possibility that control of the Senate could come down to the Loeffler-Warnock race in January. A Republican-held Senate could force Mr Biden to significantly curtail his agenda and rely extensively on executive orders to pursue his agenda. And while Democrats are still on track to retain control of the House of Representatives, Republicans have cut into their majority and picked up several seats. After flipping 43 seats in the 2018 midterm elections, Democrats have already lost seven seats and could lose as many as 12 once all ballots are counted. Mr Biden’s poor showing in Florida appears to have helped tank two House Democrats. Donna Shalala lost to Cuban American journalist Maria Elvira Salazar. And Debbie Mucarsel-Powell lost to Carlos Gimenez, a former mayor of Miami-Dade County. Despite their record as centrists, Ms Shalala’s and Ms Mucarsel-Powell’s opponents tied them to the Democratic-socialist wing of the party, which is anathema to large swathes of the Cuban American community living in Florida. House Democrats also lost seats in South Carolina, Iowa, New Mexico, Oklahoma and Minnesota.