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For weeks, Barack Obama’s campaign has had a mantra: “Do the math.” The message here is that, however close the national polls are between the president and Mitt Romney, the Republican candidate, surveys in battleground states still give the incumbent sufficient advantage to win the 270 electoral college votes needed to stay in the White House.
That is all that counts, even if he loses the total national vote – which is, at least, a possibility. “Obama is the clear favourite in a markedly close and competitive contest,” says Thomas Mann, a political analyst at the Brookings Institution, a Washington-based think-tank. “This is largely as a result of the steady lead he has enjoyed in swing states.”
Tuesday will show if the math adds up. Barring the utterly unexpected, Mr Obama is assured of carrying the west coast and the eastern seaboard north of Virginia, with the possible exception of New Hampshire, site of one of Mr Romney’s several homes.
The challenger is pretty much guaranteed the Deep South, Texas and swaths of the Midwestern heartland. That leaves the identity of the next president in the hands of just nine states. They are Nevada and Colorado in the Rocky Mountains; Ohio, Wisconsin and Iowa in the mostly industrial Midwest; Florida, home to many pensioners and Hispanics; neighbouring southern states Virginia and North Carolina; and tiny northeastern New Hampshire.
Everybody knows no Republican has become president without Ohio. But if there is a last-minute surge towards Mr Romney – like that which carried Ronald Reagan to a landslide victory over Jimmy Carter in 1980, after national polls showed them tied with a week to go – other states could be in play. The Romney camp claims these would include Pennsylvania, Michigan and Minnesota, where the Republican’s campaign has embarked on a last-minute advertising blitz.
It is generally agreed that there are more ways for Mr Obama than for Mr Romney to reach 270. He could even compensate for losing Ohio by winning five of the smaller battleground states, all of which he carried in 2008. By the same token, if Mr Romney loses Ohio, he will need close to a clean sweep in the battlegrounds.
This makes voter turnout operations, known as the “ground game”, vital. The Obama campaign claims it has more boots on the ground than Mr Romney. But enthusiasm for the former, especially among the young, is patently lower than in 2008 and overall turnout is likely to be less than the 60 per cent achieved four years ago, which was high by recent standards. The after-effects of Hurricane Sandy could depress it further.
THE EVENING UNFOLDS
This could be a far longer night than in 2008, when the networks declared Mr Obama president by 9.30pm. Even in important states where the polls close early, such as Ohio and Virginia, it may be hours before results are known. Remember Florida in 2000, when the call for Al Gore over George W. Bush was reversed in the wee small hours, and only “resolved” by the Supreme Court a full month later.
7pmPolls close in five states with 60 electoral college votes (all times are eastern standard time)
The big one is Virginia, carried by Mr Obama four years ago. It also has a hotly contested Senate race between two former governors, Democrat Tim Kaine and Republican George Allen. In Indiana, Mr Obama scored a victory in 2008 – an unlikely one, given that it had voted Republican every time since 1964. Again, a tight Senate race for the seat long held by moderate Republican Dick Lugar, defeated in his party’s primary by Tea Party adherent Richard Mourdock, could produce a bigger than expected turnout, helping the Democrat.
7.30pm Three states with 38 votes
The mother of all battles is Ohio. Indeed, the whole campaign seems to have been waged there. But North Carolina, very much of the Deep South but with a long progressive strain in the academic triangle around state capital Raleigh, also features. Mr Obama won it narrowly four years ago but would do well to repeat this time. If he does, he will be set fair.
8pm Seventeen states with 172 votes
The largest haul in one hour. The biggest single prize is Florida, perhaps Mr Romney’s best early hope of a significant gain. The Hispanic population, its Cuban element once solidly Republican, is now more diverse; its heavy concentration of pensioners worries about healthcare and social security. At least half a dozen states suffered from hurricane Sandy, to the point that the ability to vote may be affected. Illinois, which Mr Obama calls home, looks safe for the president; if it is close, he may be in trouble. Arkansas polls close at 8.30pm. Former president Bill Clinton’s magic no longer works here; the state of his birth leans Republican.
9pm Thirteen states with 153 votes
The behemoths are New York and Texas. The first will go to the Democrats and the second to the Republicans, no questions asked. However, there is much to play for in Colorado and Wisconsin. Even Michigan and Minnesota, and conceivably unpredictable Arizona and New Mexico, bear watching.
10pm Four states with 21 votes
Two are real battlegrounds – Iowa and Nevada, as different as chalk and cheese with their respective cornfields and casinos. The Hispanic population has grown rapidly in Iowa, while Nevada almost depends on Latinos to function. Getting out their vote is vital for Mr Obama.
11pm Six states with 85 votes
California is an easy call for the president, as are, probably, Washington and Oregon up the coast and his birthplace of Hawaii, out in the Pacific Ocean. Idaho and North Dakota are rock-ribbed Republican.
1am One state with three votes
If the national outcome depends on Alaska, Mr Romney will be the next president.