US voters headed to mid-term polls today that could shape the fate of President Barack Obama's agenda for the rest of his term.

Republicans need to gain six seats to win back the Senate majority they lost in 2006, which would enable them to frustrate presidential plans or at least demand a price for supporting them.

Mr Obama's Democrats currently have a 53-45 Senate majority and they can usually count on the support of two independents.

Of the 36 seats being contested, Republicans were hopeful of winning Democrat seats Arkansas, North Carolina, Colorado, New Hampshire, Alaska and Louisiana and even more confident in West Virginia, Montana, South Dakota and Iowa.

However, the under-fire Democrats could spring surprises of their own in Georgia, Kentucky and Kansas.

Republicans aren't expected to win them all, but they don't need them all, either, to make Kentucky's Mitch McConnell the next Senate majority leader - as long as he wins re-election.

Voters will also pick a new House of Representatives, choose governors in three dozen states and decide more than 100 ballot measures.

Republicans hold a 234-201 majority in the House at present and are fully expected to maintain and even extend their share of seats.

President Obama has not been welcome in many Democratic candidates' campaigns, having plummeted personally in opinion polls.

This is partly due to his unfortunate habit of being pictured playing golf when crises such as Ebola erupt and to disquiet among working people over an economic "recovery" that has not translated into improved living standards.