Daily US Times: As well as the White House, Republicans and Democrats and are locked in a tight race for control of the US Senate.
Republicans hold a 53-47 majority in the upper chamber of the Congress, meaning the Democrats are seeking a net gain of four seats.
Five seats, including some tight battleground contests in North Carolina and Georgia, are yet to be decided.
Democrats are also fighting to maintain their majority in the lower chamber of Congress, the House, and are ahead in the polls.
But with many votes still remain uncounted, the final result of both races may not be known for some time.
This year’s congressional election is running alongside the battle for the Oval Office between Donald Trump and Joe Biden.
A Democrat-controlled Senate and House would have the power to obstruct the plans of a second-term President Trump, or push through the agenda of a first-term President Joe Biden.
Of the 35 Senate seats up for grabs in this election, 23 are Republican-held and 12 are Democrat.
Senators serve six-year terms, and every two years a third of the seats are up for re-election.
Democrats had managed a net gain of one seat in the Senate election by early on Wednesday. This means three seats would have to flip to their control for the party to guarantee control of the upper chamber for the first time in six years.
John Hickenlooper, Democratic former governor, won a key Colorado seat from the Republican incumbent Cory Gardner.
Mr Hickenlooper, who stood for the Democratic party’s nomination for president, was governor of Colorado for two terms from 2011 until last year.
You may read: Trump condemned for falsely claiming election victory