[caption id="attachment_124553" align="alignright" width="163"] Mitch McConnell and his wife, former US Secretary of Labor Elaine Chao, at election night rally in Louisville, Kentucky[/caption]
In a punishing blow to US President Barack Obama, Republicans have secured a majority in the US Senate in crucial midterm elections, according to the exit polls.
The Republican Party picked up at least seven Senate seats to guarantee at least 52seats of the 100-member chamber, the results show.
They won seats in Arkansas, Colorado, Iowa, Montana, North Carolina, South Dakota and West Virginia.
Iowa Republican Joni Ernst was declared the winner over Democrat Bruce Braley and Republican Thom Tillis defeated incumbent Democratic Senator Kay Hagan in North Carolina.
According to the results, Republican candidate Tom Cotton defeated Democratic incumbent Mark Pryor in Arkansas, television networks projected.
Along with Cotton, Republicans Shelley Moore Capito in West Virginia, Mike Rounds in South Dakota, Cory Gardner in Colorado and Steve Daines in Montana also won.
Democratic Senator Mary Landrieu of Louisiana, however, forced her tough re-election fight into a runoff against Republican Bill Cassidy in Louisiana in December.
Republican Senator Mitch McConnell won his reelection fight, paving the way to be Senate majority leader.
The outcome of a closely fought race in Louisiana will be determined in a run-off in December.
The midterm elections are deciding 36 senators, 36 state governors and all 435 members of the House of Representatives.
The outcome foreshadows a tougher final two years for President Obama under a greater Republican power and influence in Washington.
Analysts believe that the poll is a referendum on the policies of the president who has lately been facing a low approval rating which was mostly driven by concern over Obamas economic record.