The Republican Party has retained control of the US Senate, it claims on Twitter, after projected wins in key races early Wednesday.
The victory leaves control of both houses of Congress unchanged, in a win for the centre-right party’s legislative agenda.
Democrats had been hoping to wrest power from the Republicans, who ahead of the elections had held a 54-44 majority in the upper house, with two independents caucusing with Democrats.
Republicans successfully defended seats that polls had shown in play in North Carolina, Indiana, Wisconsin, Missouri, Pennsylvania, Florida and Arizona, according to US broadcaster projections.
By midway through election night, only one seat had changed parties, as Democrats took a Senate seat from Republicans in Illinois.
Early returns in Nevada showed a narrow Democratic lead for the seat being vacated by retiring Senate Democratic leader, Harry Reid.