The last time a Democratic presidential candidate won Ohio's 20 electoral votes was when Bill Clinton was elected in 1996. Then George Bush won after hard-fought battles in 2000 and 2004. Ohio has elected every president since 1964. No Republican has ever been elected president without carrying Ohio, a bellwether state which combines urban and rural districts. It was home to Joe the Plumber, the ordinary American held aloft by John McCain as an example of the people who would suffer under an Obama presidency. In the end, the Democrats' foresightedness in having twice as many offices in the state as Mr McCain paid dividends.
One of three crucial swing states that has played a decisive role in presidential elections for the past 50 years. No candidate has won the White House without capturing two of three out of Pennsylvania, Ohio and Florida since 1960. It's the sixth most populous state and Mr Obama lost big to Hillary Clinton here during the primaries, with blue-collar workers appearing uncomfortable with the relative newcomer to national politics. But the state swung behind Obama in the end, and he got the prized trove of 21 electoral votes
New Mexico's 5 electoral votes have swung between Republicans and Democrats, voting narrowly for Bush in 2004, and equally narrowly for Gore in 2000. The Democratic governor, Bill Richardson, who has Hispanic roots, served in the Clinton administration and initially supported Hillary Clinton before switching allegiance to Obama and helping turn red to blue.
Iowa was where it all began for Mr Obama. It was here, at the beginning of January, that he won the first Democratic caucus, bumping Hillary Clinton, the assumed standard-bearer of the Democratic Party into third place and signalling his intent to become the first black occupant of the White House. The victor here is usually a toss-up; last time around Mr Bush won by a whisker. But the grassroots network Mr Obama had laid all those months ago served him well, and he carried the seven electoral votes up for grabs amid the famed cornfields.
In the 2004 election, Vermont – a sparsely populated land of maple syrup and granola – was the third most Democratic state. There was never any doubt that its three electoral votes were safely in Mr Obama's column – it has been Democratic in the past four elections. A fiercely independent state. it is also one of the most liberal.
New Hampshire is special in the American electoral calendar because the first primary of the campaign has been held in the state since 1920. Mr Obama won its four electoral college votes after losing a shock result in January's primary to Hillary Clinton after being expected to win handily on the back of his victory in Iowa.
Delaware has been hotly contested in most presidential races for decades and was a reliable bellwether until 2000, voting for every presidential winner from 1952 to 1996. But in the past two elections it leant more heavily to the Democrats: Al Gore and John Kerry won it easily. It was never likely to be anything but solid Obama with its Senator Joe Biden on the ticket as his running mate.
This has been the most Democratic state in the country for the past 10 presidential elections and it was no surprise that Obama swept its 12 electoral votes. Massachusetts has been a factory for producing Democratic Party presidential candidates, including John Kerry who won the state with a 25-point margin in 2004. Other presidential candidates from the state include Ted Kennedy, Michael Dukakis, Paul Tsongas and the Republican Mitt Romney.
A strongly Democratic state whose seven electoral votes were carried by Mr Obama. Wealthy Connecticut voters have traditionally voted Democrat and it is the home state of Senator Joe Lieberman, picked by Al Gore as his vice-presidential running-mate in 2000. The pair carried the state by 56 per cent to 38 per cent for George Bush. Lieberman left the Democratic Party in 2006 to run as an independent.
Maine's 4 electoral votes were expected to go to Mr Obama. But the former president George Bush Snr has a holiday home in Kennebunkport, Maine, and the state has swung between Democratic and Republican candidates in the past. Mr Bush Snr won in 1988, and Bill Clinton in 1996.