McConnell, the top Republican in the Senate, is nearly as unpopular with Republicans as he is with Democrats, and a victory by 35-year-old rising star Grimes would send shock waves through US politics. He looks likely to survive, however, through a combination of guile and deep pockets.  Begich rode the Obama wave into the Senate in 2008, winning this fiercely Republican state by just 1pc, despite his opponent’s conviction on felony corruption charges. His personal approval ratings are very respectable for a Democrat in Alaska, but that may not be enough to save him.  Braley was long the frontrunner in Iowa, but has made some big mistakes, including disparaging farmers in an agricultural state. By contrast his opponent, a former hog farmer and Iraq war veteran, has put together an effective TV campaign, been endorsed by Mitt Romney, and is now the favourite.  Hagan, another elected on the Obama wave, has fought tooth and nail to hold on to her seat. In this Republican-leaning state, that has meant repeatedly distancing herself from Obama. If she wins, Democrats counting on her survival won’t begrudge her for it.  Landrieu is another incumbent Democrat in an uphill re-election battle. But with neither candidate expected to get a required 50 per cent of the vote, this race is likely to go to a run-off vote in December. Depending on results elsewhere, it could be Louisiana that settles the Senate question.  Democrats never thought they’d have to worry about Colorado in 2014. The western state is 21% Hispanic, Obama won it twice, and incumbent Udall looked strong. Yet Gardner has been consistently polling ahead in recent weeks. If the Democrats lose Colorado, it will be a sign they’re in deep trouble.  Republican plans to re-take the Senate were banking on victory in Kansas. As recently as a month ago it seemed a sure thing, but the campaign of Greg Orman, an independent who once funded Democrats, has caught fire. If he wins, Republican hopes of taking back the Senate could be dashed.
With midterm elections approaching, we look at the key seats Republicans need   to "flip" to retake the Senate on November 4