The Republican Party has won control of the Senate in the US mid-term elections, increasing its power in the final years of Barack Obama’s presidency.
The party took Arkansas, Colorado, Iowa, Montana, North Carolina, South Dakota and West Virginia.
Republican Senate leader Mitch McConnell will lead the chamber.
The party is also set to strengthen its majority in the lower House of Representatives.
As the early results came in late on Tuesday, it became clear the Republicans had made convincing gains in the roughly one-third of the 100 Senate seats up for election.
The party retained seats in Alabama, Georgia, Kansas, Maine, Mississippi, Nebraska, Oklahoma, South Carolina and Tennessee.
One of the key early results came in Kentucky, where Republican Senate Minority Leader McConnell fended off Democrat Alison Lundergan Grimes
Mr McConnell will now become the Senate majority leader.
“I’ve heard your concerns, I’ve made them my own, you will be heard in Washington,” he said as he declared victory.
“When you get right down to it that’s what this campaign was really all about. It’s wasn’t about me or my opponent. It was about a government that people can no longer trust.”
As well as in the Senate races, the Republicans had a strong showing in the election for the 435 members of the House of Representatives, where they are projected to increase their majority.
In Florida and Wisconsin, Republican governors have survived tough re-election battles.
Now that they control both houses of Congress, the Republicans have the power to shut down Mr Obama’s policies in the last two years of his term.
For the past year, political gridlock in Congress has reached historical levels and analysts say this win could make the situation even worse before the president poll in 2016.