Foreign Editor, Paddy Smyth, provides a guide to watching the results come in
TONIGHT'S US presidential election will be decided in a few battleground states. If, as opinion polls predict, Barack Obama captures such critical states as Virginia, Florida, Ohioand Indiana- where polls close by 1am Irish time - he will be well on his way to winning the 270 electoral votes (see panel on electoral votes system) that will put him in the White House before the western half of the country finishes voting.
Ohio(20 electoral votes), a state battered for years by unemployment and plant closings: in this working-class bastion Obama is leading McCain by 49 per cent to 45 per cent among those likely to vote.
Florida(27): considered a likely win for Republicans not long ago, but now McCain is trailing, 50 per cent to 46 per cent.
In both states, Obama has opened commanding leads over McCain among women, young people, first-time voters, blacks and other minorities.
Virginia(13): Bush won by nine points in 2004 in a state that has not gone Democratic in a presidential since 1964. But the trend has been toward Democrats in recent state elections amid dramatic growth. Obama leads by four points.
Indiana(11): Bush beat Kerry by 20 points in 2004 in a state that last voted for a Democrat in 1964. However, it borders Obama's home state of Illinois and he has poured resources into his Indiana campaign. Obama is ahead 1.5 points in the latest polls.
Indeed, as the map above shows, two of these four states should be sufficient to bring him from the 238 "solid" votes he should secure in safe Democratic states over the winning 270 line.
In 2004 11 states - Oregon, Nevada, Colorado, New Mexico, Minnesota, Wisconsin, Iowa, Michigan, Pennsylvania, New Hampshire, and Ohio- representing just over a fifth of the electoral college votes - were decided on margins of victory of less than 5 per cent ("marginals").
Such has the tide apparently turned against the Republicans that of the five of those marginals that went to George Bush - Nevada, Colorado, New Mexico, Iowaand Ohio- polls suggest only Ohiois in the marginal camp this time, and even there Obama has a four-point lead in the polls. All the rest show poll leads for Obama over 6 per cent.
Of the six marginals that went to the Democrats' John Kerry in 2004 - Oregon, Minnesota, Wisconsin, Michigan, Pennsylvania, and New Hampshire- all but Pennsylvanianow manifest solid leads for Obama by over 9 per cent while the latter leans by 7 per cent to Obama. In Oregonand Michiganhe leads by 16 and 13 per cent respectively.
Pennsylvaniawith its 21 electoral college votes has been a particular focus of McCain in recent weeks. He hopes to break from the party traditionally Democratic working-class white voters hurt by the financial crisis, although they gave Kerry a 2.5 per cent victory margin in 2004 and Al Gore 4.2 per cent in 2000.
Tallying electoral college votes across the entire US in solid Republican and Democratic states (where either candidate has a lead of over 9 per cent) suggests that Obama can already be confident of solid support in some 238 of the 270 electoral college votes needed to win, while McCain can only be assured of 118. In states "leaning" towards either candidate (with a margin of 5-9 per cent) Obama can hope to pick up a further 40 votes to McCain's 14, pushing the former well over a majority position.
On the basis of such polling nine states remain marginal - Florida, North Carolina, Missouri, Indiana, Georgia, Montana, Arizona, Virginia, and Ohio- with only Missouri, Indiana, Georgiaand Montanashowing a McCain lead. All nine marginals voted for Bush in 2004. They represent 125 electoral college votes.
• Poll figures from Real Clear Politics poll averages
Setting standards
Barack Obama'schallenge:
When Bill Clinton beat President George H W Bushin 1992 he won by a margin of 5.6 percentage points.
That was less than H W Bush's7.7 point win over Massachusetts Governor Michael Dukakisin 1988, and than Clinton's8.5-point win over Senator Bob Dolein 1996.
Even higher on the landslide roster was Californian Governor Ronald Reagan's9.7 point victory over President Jimmy Carterin 1980 and Gen Dwight Eisenhower's10.9 point win over Adlai Stevensonin 1952.