US mid-terms: Republicans poised to take Senate
The Republican Party is on the verge of taking the US Senate, where they need just one more seat to win control of the chamber, initial results in the US mid-term elections show.
The party has already won five Senate seats - in Arkansas, Colorado, Montana, South Dakota and West Virginia.
In Florida and Wisconsin, Republican governors have survived tough re-election battles.
The Republicans are also projected to strengthen their hold on the House.
One of the key early results came in Kentucky, where Republican Senate Minority Leader McConnell fended off Democrat Alison Lundergan Grimes, positioning himself to lead the chamber should the Republicans win the majority.
"I've heard your concerns, I've made them my own, you will be heard in Washington," he said.
"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 polls close across the country, early results indicate a number of both Democratic and Republican Senate incumbents have held onto their seats.
Projections show Republicans have retained seats in Alabama, Georgia, Kansas, Maine, Mississippi, Nebraska, Oklahoma, South Carolina and Tennessee.
Democrats have retained seats in Delaware, Massachusetts, New Jersey and Rhode Island.
They have also held on to the key Senate seat of New Hampshire.
In Louisiana - a key state for the Republicans to win - the contest for the Senate will go to a run-off in December after the Democratic incumbent failed to win an outright majority.
As well as about a third of the 100-seat Senate, all 435 members of the House of Representatives, 36 out of 50 state governors, and countless state and local offices are up for election.
In the governor elections, Democrat Tom Wolf has unseated the Republican incumbent Tom Corbett.
But elsewhere the Republicans fended off strong challenges.
In Arkansas, Republican Asa Hutchinson defeated Democrat Mike Ross.
Wisconsin Republican Governor Scott Walker, who is considered to have presidential aspirations, fended off Democrat Mary Burke.
In Florida, Republican Rick Scott held off a challenge from Democrat Charlie Crist, himself a former Republican governor of the state who switched parties.
Republican incumbents also retained their seats in Alabama, Iowa, Michigan, New Mexico, Ohio, Oklahoma, South Carolina, South Dakota and Tennessee.
The Democrat Andrew Cuomo has been re-elected as governor in New York. Democratic incumbent governors also won re-election in New Hampshire and California.
Throughout the campaign, the Democrats have battled to stay ahead as President Barack Obama's approval ratings fell to the lowest they have been since he was elected.
Many analysts have predicted a Republican victory as Mr Obama's popularity rate has failed to climb much above 40%, despite recent improvements in the economy.
If the Republicans succeed in taking control of the Senate from the Democratic Party, Mr McConnell is set to become the majority leader.
As the Republicans already have a convincing hold over the lower House of Representatives, a win in the Senate would give them the power to shut down Mr Obama's policies in the last two years of his term.
Analysis: Jon Sopel, North America editor
I have spoken to Democrats and Republicans and they all said the same thing - they were sick of the partisan posturing, the gridlock, the inability to work together, the dysfunctional relationship between Congress and White House, between legislature and executive.
All of which begs the question - what difference will it make if the Republicans do take control of the Senate?
Some are predicting that it will be gridlock on steroids. In other words, just like before - only worse.
Others, who've clearly read Voltaire's Candide and based their philosophy on the ever-optimistic Dr Pangloss, think we will go to the sunny uplands of politics.
Aside from Mr Obama's unpopularity, there is no single issue that dominates this mid-term poll.
Instead voters have been swayed by a broad variety of concerns including the economy, the environment, immigration, foreign policy, abortion and healthcare. In addition, the Republicans have sought to make the election a referendum on Mr Obama's policies and performance.
Across the board, voters have expressed their dissatisfaction with both parties' inability to co-operate in Congress and the resulting gridlock this has caused.
Six Senate races to watch
- North Carolina - Kay Hagan v Thom Tillis
- Arkansas - Mark Pryor v Tom Cotton
- Colorado - Mark Udall v Cory Gardner
- Georgia - Michelle Nunn v David Perdue
- Iowa - Joni Ernst v Bruce Braley
- Kansas - Greg Orman v Pat Roberts