Republicans became dominant in the Senate today and extended their majority in the House of Representatives, gaining a stranglehold on the Congress levers of power.

They also claimed control of a number of previously Democrat-inclined states in gubernatorial contests that confirmed the negative poll ratings experienced by President Barack Obama.

Many Democratic candidates went so far as to distance themselves from their own White House incumbent, although this brought them no joy.

The vote gives Republicans momentum heading into the 2016 presidential race, which becomes the focus of US politics for the next two years.

Mr Obama now assumes lame-duck status for the latter period of his term in office, which offered so much when he became the first African-American president in 2008 and was then comfortably re-elected in 2012.

He is now dependent for the first time on doing deals with a Republican-led Senate after the party made at least seven gains from the Democrats.

This could increase still further after a December 6 run-off in Alaska, where Republican Dan Sullivan leads outgoing Democratic senator Mark Begich, although neither candidate won a majority.

Republicans made the Obama presidency the core issue of their campaigns, tapping into a well of discontent among Democrat supporters alongside the usual far-right obsessions of Tea Party advocates.

"It's a reflection of the president's lack of leadership, his lack of leadership abroad, his lack of leadership at home," said Republican New Jersey governor Chris Christie, who is flirting with the idea of putting his name forward for his party's 2016 presidential candidate.

Among the Democrats' few bright spots were the re-election of New Hampshire senator Jeanne Shaheen and governor Maggie Hassan and Tom Wolf's overturning of Pennsylvania Republican governor Tom Corbett.

Republicans picked up governors' seats in usually reliably Democratic states such as Illinois, Maryland and Massachusetts and will have been especially encouraged by victories in battleground states Florida and Ohio that can often sway presidential races.

In the House of Representatives, they look to be on track to exceed even the 246 seats they held during Democrat president Harry S Truman's administration in the late 1940s.

Petitions have their moment in the sun

US voters have the opportunity, as well as electing public officials, to propose policy changes on the basis of public petitions submitted to the electorate.

While legalisation of marijuana is often a major concern, so are unceasing attempts by religious and sundry other fanatics to restrict women's right to control their own fertility.

Voters in Colorado and North Dakota rejected measures that could have led to bans on abortion rights.

The Colorado proposal would have added "unborn human beings" to the state's criminal code. It was the third measure on Colorado ballots in recent years seeking to accord personality to the unborn.

North Dakota voted against an amendment that would have declared in the state constitution "the inalienable right to life of every human being at every stage of development must be recognised and protected."

However, in Tennessee, the electorate approved a measure to give state legislators more power to regulate abortion, which opponents fear could lead to tough new laws that would jeopardise women's ability to terminate pregnancies.

Voters in Alaska, Arkansas, Nebraska and South Dakota - all Republican-leaning states - backed increases in the state minimum wage at a time when Republicans in Congress have blocked an increase in the pay safety net.

Washington state approved a measure to extend background checks on gun sales and transfers to private transactions and many loans and gifts.

Voters in Oregon and federal capital Washington DC supported measures allowing recreational use of marijuana by adults, joining the company of Colorado and Washington state, where that decision was made two years ago.