US midterm election battles to watch

Senate: Kentucky (Republican) Likely Republican hold Mitch McConnell – the would-be Senate majority leader if Republicans pick up the six seats they need to take control – has spent vast sums of GOP cash along with outside support money in this traditionally red state – putting it on track to be one of the most expensive races in this cycle. Despite the spending, he has failed to command a consistently strong lead over Kentucky secretary of state Alison Lundergan Grimes. Her failure to say whether she voted for an unpopular Obama has strengthened his hand in winning a sixth term.

Senate: New Hampshire (Democrat) Leaning Democratic hold Former Republican senator Scott Brown was drawn into a discussion about his knowledge of New Hampshire geography by a journalist moderator in a televised debate last week, highlighting his blow-in status from neighbouring Massachusetts, where he failed to win re-election, and confirming his status by political rivals as "a carpetbagger". Democratic senator Jeanne Shaheen is popular when the Washington political establishment is not, and she enjoys a slight lead.

Senate: North Carolina (Democrat) Leaning Democratic hold The Republican challenger, state house speaker Thom Tillis, has faced about $26 million in negative adverts approved by Democratic senator Kay Hagan and funded by outside groups in one of the nastier and costliest campaigns of the mid-terms. She has tied him to an unpopular state government and he has tied her to an unpopular national government.

Senate: Kansas (Republican) Leaning Republican loss Independent Greg Orman could complicate the GOP's hopes of retaking the Senate in a state that has not sent a non-Republican senator to Washington since 1932. Holding a slight lead in the polls, Orman has benefited from Republican veteran Pat Roberts suffering in a hard-fought GOP primary fight and question marks over his home-state loyalty and residency. Orman hasn't said which party he would vote with in the Senate, so neither party can count on his support.

Senate: Georgia (Republican) Leaning Republican hold This red state could result in Senate control not being decided until January, as neither Republican, businessman David Perdue, or Democrat Michelle Nunn, daughter of former governor Sam Nunn, are expected to win 50 per cent. Perdue's support for outsourcing jobs overseas during his career was brought up in the campaign but he is favourite to take the seat of retiring GOP senator Saxby Chambliss.

Senate: Iowa (Democrat) Leaning Republican gain Republican state senator Joni Ernst has come from well behind to lead with clever, humorous campaigning and mis-steps by Democratic rival Bruce Braley, who was thought guaranteed to hold retiring senator Tom Harkin's seat for his party in a state that Obama won twice.

Senate: Colorado (Democrat) Leaning Republican gain Another state that Obama won in the 2008 and 2012 elections, but the president, suffering some of the worst approval ratings of his six-year presidency, has avoided Colorado. Sitting Democrat Mark Udall has been lambasted for his negative "war on women" ads against Republican congressman Cory Gardner, who has moderated his previous conservative positions to be seen as a reasonable alternative.

Senate: Alaska (Democrat) Leaning Republican gain Democratic senator Mark Begich went much further than the party's other candidates to distanced himself from Obama when he described the president as "not relevant" given that "he's gone in two years." This hasn't convinced people in deeply conservative Alaska where his Republican rival Dan Sullivan has a small lead.

Senate: Louisiana (Democrat) Leaning Republican gain Democratic senator Mary Landrieu is in trouble in another state that has traditionally favoured Republican presidential candidates, but because she is facing two Republicans, congressman Bill Cassidy and Tea Party candidate Rob Maness, she could end up in a run-off early next month if no candidate reaches 50 per cent of the ballot.

Senate: Arkansas (Democrat) Leaning Republican gain Despite support from popular former president Bill Clinton in his home state, sitting Democrat Mark Pryor is polling behind Republican congressman Tom Cotton, a veteran of the American wars in Iraq and Afghanistan. Pryor was damaged by attacking Cotton on Ebola, and later struggled to answer whether Obama was handling the crisis well, with some painful "ummmms" in response to a reporter's questions.

Governor: Wisconsin Likely Republican hold This gubernatorial battle is worth a mention as it features the only one of the current crop of potential Republican presidential contenders in 2016 seeking re-election – Scott Walker. He survived a recall election in 2012 called by liberal voters in the mid-western state who were unhappy with his attack on unions, tax cuts and cuts to education and healthcare budgets. This made him a favourite of the party's conservative Tea Party grassroots, putting him in the frame for a future White House run. He has to win re-election first though and he is in a tough battle with Democrat Mary Burke, a businesswoman.