All 435 seats in the House are up for grabs. Democrats need to win net 15 seats to win control.

A third of the Senate’s 100 seats are being contested - Democrats need to win net six seats to gain control.

There are also 36 races for governorships.

Key races - House
The Democrats need to gain a net total of 15 seats to regain the House of Representatives for the first time since 1994. They have the potential to pick up 20 or more seats including districts in the states of California, Colorado, Illinois, Indiana, Indiana, Iowa, Ohio, Pennsylvania and Texas. The Republicans are hoping to make gains in a handful of districts, including one in Ohio.

Key races - Senate
The Democrats will be trying very hard to win the six extra seats they need to gain control of the US Senate. We look at a dozen of the most interesting races.

Key races - governorships
Of the 50 governorships in the United States, the Republicans currently hold 28 to the Democrats’ 22, so if the Democrats want to gain a majority of the governors’ mansions, then they need to win four (net) of the 36 gubernatorial elections on 7 November.

source: BBC