To recap quickly, Republicans have picked up three seats in Arkansas, South Dakota, and West Virginia, but they still need to defend two of their own seats to win control of the Senate.

Texas senator and Tea Party favourite Ted Cruz would be a pivotal figure in a Republican Senate, and he's been telling the Washington Post, external he's in no mood to compromise.

President Barack Obama has only a 40% approval rating in the key state of Iowa, according to a preliminary ABC exit poll.

Republican Senate candidate Mike Rounds, projected winner in South Dakota, served as the state's governor for eight years, from 2001 until 2011.

Image source, AP

Republicans pick up their third Senate gain of the night in South Dakota, according to ABC News, and need just three more to control Senate.

Image source, Getty Images

Democratic Senate candidate Alison Lundergan Grimes thanked her supporters following her defeat by Senate Minority Leader Mitch McConnell.

Here's a short video reminder of the Senate seats that matter tonight: US mid-terms: Senate races to watch

Republican Mitch McConnell spoke to a cheering crowd shortly after winning re-election to his Kentucky Senate seat.

Paul Danahar, BBC News Washington

tweets, external: If Democrats lose the Senate Obama loses the domestic agenda. Will that lead him to try shaping instead of just reacting to world events?

Democratic strategist Ben LaBolt tells the BBC he dismisses the suggestion that the election is a rejection of President Barack Obama's agenda.

"There's general disgust with what voters see as inaction in Washington."

Tara McKelvey
BBC News, Kansas

One of the biggest mysteries of this campaign season is Kansas independent Greg Orman, who might vote with Democrats if he's elected to the Senate - and might not.

In Overland Park, Kansas, Lynda Allen says; "I think he wants to go in and do his own thing."

Her daughter, Maddie Allen, interrupts, saying: "He'll figure out what's best for Kansas."

President Barack Obama has invited Congressional leaders from both parties and both houses of Congress to the White House on Friday to discuss a path forward following the mid-term election, ABC News reports.

To sum up where we are, Republicans have made two crucial Senate gains in Arkansas and West Virginia, but have failed to snatch New Hampshire. However, Mitch McConnell has held his seat in Kentucky, after looking like he was in trouble earlier in the year.

Image source, Reuters

Supporters of Florida's Republican Governor Rick Scott wait at a venue in Bonita Springs for the results of the poll.

That means they now have two of the six Senate gains they need to take control of the upper chamber.

Republicans have made their second Senate gain of the night, this time in Arkansas with the victory of Tim Cotton over Democratic incumbent Mark Pryor, according to the Associated Press news agency.

Barbara Plett Usher
BBC state department correspondent

tweets, external: Former NH senator Judd Greg expects #GOP wave, says once congress controlled by 1 party shd be able to govern better

In her concession speech, defeated democratic Senate candidate Alison Lundergan Grimes says her "fight was worth it", and that it sent a message that Kentucky needs to address issues like fair pay and bringing good jobs back to the state.

Republicans have held on to several Senate seats across the US, according to ABC News.

They are Senator Jeff Sessions in Alabama, Senator Susan Collins in Maine, Senator Thad Cochran in Mississippi, Senator Jim Inhofe in Oklahoma, and Senator Lamar Alexander in Tennessee.

The former Republican governor of Mississippi, Haley Barbour, told the BBC that if his party wins big tonight it will be a repudiation of President Obama's policies. But he added this would not mean a full endorsement of Republicans by voters.