As Georgia may have to hold run-off elections for both its seats, the balance of power in the U.S. Senate may not be decided until January, according to BBC.
As required by state election law, no candidate in either race has polled 50 percent.
The run-off elections are scheduled to take place on 5 January, two days after the meeting of the new Senate.
At present, the Republicans have a lead of 53 to 47 in the Senate and appear on track to retain control, with a loss of one seat overall so far.
The Democrats had high hopes of winning the four seats they needed to take over, but their seats were held by several Republican incumbents.
However, if the Democrats were able to win both seats in the historically Republican state of Georgia, this would lead to a 50-50 tie in the Senate.
In one of the Georgian Senate races, in his fight against Libertarian Party Democrat Jon Ossoff and Shane Hazel, incumbent Republican David Perdue falls just shy of 50 percent of the vote, with 98 percent of the votes counted.
Ben Fry, campaign manager for Mr. Perdue, said that if overtime is required when all the votes are counted, we are ready and we will win.
But the Ossoff campaign predicted that the Georgians will send Jon to the Senate when a runoff is called and held in January. Mr Perdue is actually behind by 2 percentage points.
Democrat Raphael Warnock gained 32.8 percent in Georgia's other Senate race and will go into a run-off against Republican Senator Kelly Loeffler, who trailed him with 26 percent.
In Maine, Susan Collins, the moderate Republican incumbent, staved off Democrat Sara Gideon 's fierce challenge.
For six years, Democrats have not had control of the Senate.