The Republican Party has taken control of the Senate by picking up at least six seats from the Democrats
They have also strengthened their grip on the House of Representatives
Ballot initiatives expanding marijuana use and increasing minimum wage passed in some states
The economy, government dysfunction and President Obama's unpopularity were key issues
The Republican response has been swift, with national chairman Reince Priebus congratulating his candidates.
"The American people have put their trust in the Republican Party, sending a GOP majority to the US Senate... our party's principles and message resonated with voters across the country. This was a rejection of President Obama's failed polices and Harry Reid's dysfunctional Senate."
Image source, ReutersChad Pergram, Fox News
tweets, external: McConnell now has toughest job in Washington as he becomes Majority Leader. Senate requires supermajority to do most business (60).
And the night is fast getting better and better for the Republicans. ABC News projects Joni Ernst has beaten Bruce Braley in Iowa - which would bring the Republican majority to 52.
More Republican joy in Georgia where Nathan Deal has won the governor race, beating Democrat Jason Carter, grandson of former president Jimmy Carter.
Republicans have won control of the Senate with a win by Thom Tillis over Kay Hagan in North Carolina.
On CNN, Washington correspondent Jake Tapper notes - "It looks like for the first time in history, 100 women are in the House".
Former Texas Republican Senator Kay Bailey Hutchison tells the BBC World Service the party needs to have a better message on immigration if they want to capture the Hispanic vote in 2016.
James Richardson tweets, external: "It took a decade, but Republicans have finally toppled John Barrow, the last remaining white congressional Democrat from the deep south".
Image source, APAnother Senate result - Pat Roberts has fended off a challenge from independent Greg Orman in the very closely watched race in Kansas.
The Associated Press news agency confirms David Perdue wins the Georgia senate race, as Michelle Nunn concedes in front of a crowd of supporters.
Image source, ReutersThe BBC's Jon Kelly outlined some scandal-hit politicians who looked poised to win re-election. Scott DesJarlais, a doctor who campaigned on pro-life issues but pressured his wife and mistress to terminate pregnancies, has won his bid for re-election in Tennessee. So too has Michael Grimm, the Staten Island congressman who is facing 20 criminal counts.
Anthony Zurcher
BBC News
The District of Columbia voters approve a ballot initiative legalising the possession of small amounts of marijuana for personal use. As Vox's German Lopez points out, however, the US Congress still has an opportunity to review - and reject, external - the measure before it becomes law in the nation's capital.
The first results from the West Coast have begun - Democrat Jerry Brown is re-elected governor in California.
While they may not be representative of all Americans, exit polls do provide some useful insight into the minds of voters. Today's polls show voters are deeply pessimistic about the direction of America and its politics.
Results coming thick and fast now. Wisconsin Governor Scott Walker has won re-election. As Rajesh Mirchandani explains in a video outlining what tonight's results could mean for the 2016 presidential election, Mr Walker is among the many Republican named as possible presidential candidates for 2016.
CNN and ABC are projecting Republican David Perdue to win against Democrat Michelle Nunn. It is not a pick-up seat for the Republicans but there were hopes among Democrats they could steal it and this will further weaken then chances of retaining their majority.
Meanwhile in Virginia, Democrat Mark Warner is neck-and-neck with Republican Ed Gillespie. Mr Warner leads by only 3,400 votes out of more than two million votes, with 99% precincts reporting. The result has confounded expectations as even the Republican party officials had not expected the race to be this close.
NPR social media editor Wright Bryan tweets, external: "Who's the youngest of them all? Saira Blair, 18, is ready to make a difference in West Virginia". She is now the youngest elected state house representative.
Image source, NPR
Image source, APMr Gardner attacked his opponent for voting with President Obama.
Given Colorado's recent Democratic momentum in presidential elections, Republicans had been watching the race closely as as a test case for whether traditional rural conservatives like Mr Gardner can still win state-wide elections in places, such as Colorado, that seem to be slipping out of their grasp, the BBC's Anthony Zurcher wrote after visiting Colorado in September.