U.S. Republican Senator Dan Sullivan of Alaska won re-election, Edison Research projected on Wednesday, leaving control of the Senate to be determined in January by two runoff elections in Georgia.
Sullivan, 55, defeated Al Gross, an independent who ran as a Democrat in an election that some political analysts had seen as a potential opportunity for Democrats to capture a Republican seat.
Coming a day after Republican Senator Thom Tillis won re-election in North Carolina, Sullivan's victory confirms that Democratic hopes of winning a majority of seats, and with it the power to support Democratic President-elect Joe Biden's agenda, will come down to two Georgia elections scheduled for Jan. 5.
With Biden's White House victory, Democrats need to pick up three Republican Senate seats to hold 50 Senate seats, with Vice President-elect Kamala Harris wielding the tie-breaking vote.
Biden has surpassed the 270 Electoral College votes needed to defeat Republican incumbent President Donald Trump.
Democrats won Republican seats in Arizona and Colorado in last week's election. But they lost a seat in Alabama, reducing their gain to a single seat.
In Georgia, Republican Senators David Perdue and Kelly Loeffler face challenges from Democrats Jon Ossoff and Raphael Warnock, respectively.