These states are not firm supporters of either political party. Their electoral college votes (which decide on who gets to be president) are up for grabs this year.
Here's a look at eight key swing states and how many electoral college votes they hold compared with the 2008 election:
9 electoral votes (unchanged)
It could be the One That Counts if Romney wins in New Hampshire, Virginia, Florida and Wisconsin. The ethnically mixed state is getting more so, as the Hispanic voting population grows. But will they vote? Last election it seemed so, with a big, historic bull’s eye for Democrat Obama. This time polls say it’s iffy. Romney is putting faith in the evangelical vote, which may not favour a Morman, and the military. Obama’s organizers are focusing on luring voters to the polls.
29 electoral votes (increase of two)
The vote-rich Suntan State turned blue for Obama in the last election by fewer than 3 percentage points, possibly due to minority support: 96 per cent of the African-American vote, 57 per cent of Latino voters, and 52 per cent among independents, according to exit polls. But Florida has a strong bedrock Republican population, and Romney is currently neck-and-neck with Obama in opinion polls. Maverick conservative candidates could trim his numbers with right-wing voters.
Six electoral votes (decrease of one)
After tireless campaigning in the last election, Obama owned Iowa by a margin of 10 percentage points. But on closer scrutiny, the farm state has a split political personality: Democratic northeast and Republican southwest. Iowa’s main newspaper delivered a shock by switching support to Romney on economic grounds, and his strategists are working to peel away socially conservative rural folk who bristle at abortion and gay marriage.
Six electoral votes (increase of one)
With a high-roller’s knack for picking winners, Nevada has gone for the victorious candidates. In the last election voters outdid themselves, giving Obama a double-digit margin over John McCain. This time, maybe not so much. In spite of nearly 12 per cent unemployment, Obama still leads Romney in some polls, on economic issues. But Nevada’s devastated economy could yet be Romney’s ace in the highest-stakes game of political poker.
Four electoral votes (unchanged)
The “Live Free or Die” motto made this a famously independent-minded — some would say ornery — state. Romney hopes his freedom-from-government agenda will resonate here. Although New Hampshire handed Obama an overwhelming victory in the last election, he can’t take it for granted this time round. Romney, with strong ties to New England, is pressing Obama’s weakness on the deficit and touting his own chops as a free marketer.
18 electoral votes (decrease of two)
In the ultimate swing state, and birthplace of the hotdog, candidates are hungry for a large helping of juicy electoral votes. Obama had a comfortable win last time, but concentrated in the industrial northeast. Romney is aiming at more rural areas and towns such as Cincinnati, which formerly voted Republican. Ohio has benefited from Obama’s auto bailout, but Romney is battling back with attack ads claiming Chrysler is outsourcing Jeeps to China.
13 electoral votes (unchanged)
In a state where black voters were penalized by fees and literacy tests until 1965, it’s the minority vote that now tips the balance. Obama was the first Democratic presidential candidate to win Virginia since 1964, backed by Hispanics and African-Americans. But Republicans clawed back three House seats from Democrats in 2010. Romney hopes the force is still with him. His emphasis on the shrinking navy in the last debate was aimed at Virginia’s Naval Station Norfolk.
10 electoral votes (unchanged)
Wisconsin gives and it takes away, often unpredictably. Although Obama won a resounding victory in the last poll, voters have a short attention span. A bitter battle over the attempted firing of far-right Republican Governor Scott Walker added to the bipolar politics, and his supporters declared that the Democrats were crushed. Romney’s running mate, Paul Ryan, is also a homeboy here. But Obama’s apparent strength in the Midwest makes this a guessing game.