Republicans across the country are hoping to benefit electorally from disappointment with Barack Obama and, in particular, the problems in the US economy. The GOP is fighting hard to win back both the House of Representatives and the Senate.
These elections, involving the most expensive midterm campaigns in US electoral history, will be seen as a political virility test of the Tea Party conservative movement, which has already notched up several surprising victories over more moderate Republican candidates in the primaries.
In total, all 435 members of the House of Representatives are up for election, together with a third of the 100 seats in the Senate (37 in all). There are also 37 gubernatorial elections being contested.
Not since 1962 has the political party of a sitting president gained the majority of seats in the House during midterms.
The following list, though by no means exhaustive, gives an idea of some of the key races to watch.
The results will be known soon after voters go to the polls on 2 November.
14. Alaska – Senate
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