In the Democrat corner...
Obama was born to a white woman from Kansas and a Kenyan philanderer sent to Hawaii on a scholarship. His father never really left his first wife, Kezia, in Kenya, even when he married Obama's mother. "How and when the marriage occurred remains a bit murky, a bill of particulars that I have never quite had the courage to explore," Obama has said.
Already the greatest fund-raiser of all time for a presidential candidate. He hauled in more than $265m (£136m) by the end of April, compared to nearly $97m for McCain.
He has no pets, although his children, aged nine and six, want a dog.
For a man of 46, Obama's health is very good. His doctors say he has no "excess body fat" as he is a regular jogger. His history of smoking (and lying about quitting when he was still puffing last August) may come back to haunt him with the health police. For now his "bodyman", Reggie Love, carries a pack of emergency Nicorettes.
Obama works out on the basketball court every morning and plays the game every chance he gets with Craig Robinson, his brother-in-law, a professional basketball coach. The hoops give him street cred in urban America.
From the start, Obama is promising a blizzard of reforms, beginning with closing Guantanamo, ending torture and shutting down the war in Iraq. Health care will get a top to bottom overhaul, perhaps led by Hillary Clinton, as will education. On climate change, expect the US to take a leadership role.
A model of discretion usually, Obama shot himself in the foot when he said rural white voters "cling" to guns and religion when the economy goes bad.
A fastidious eater who toys with the poached salmon on his plate and nibbles lettuce, but for the cameras he puts on a show of eating big breakfasts at diners and quaffing beers in sports bars.
The Obama camp like to call McCain, McSame when it comes to Iraq, because his policies mimic those of George Bush. But Obama's offer to talk to the Iranian leadership disturbs Jewish voters, even though two thirds of Americans back the President meeting leaders of enemy countries. On the electoral acid test of Israel, Obama says: "You will not see, under my presidency, any slackening in commitment to Israel's security."
When Obama plays basketball on election day, he wins. He played the day of the Iowa caucus and South Carolina primary, and won both contests. He did not play the day of the New Hampshire primary and Nevada caucus, and lost. He recently told 60 Minutes that playing basketball is an election day "rule" now. And yes, he also played on Tuesday.
The storm over the Rev Jeremiah Wright, who said God had damned America in 9/11 because of slavery and the genocide of the Indians, nearly did for Obama. Expect the Republicans to return to the pastor, as well as his association with Tony Rezko, being tried for corruption.
Poor Obama. Wherever he goes he knows that at least half of the audience actually believe he is a Muslim masquerading as a Christian. Not good in deeply religious America. Anonymous emails accuse him of being a terrorist supporting Muslim fundamentalists. This spells trouble since Christian extremists and Jewish voters represent key voting blocs.
If he wasn't running for the White House, Obama could easily turn his hand to writing. His memoir, Dreams from My Father, written after he became the first black editor of the Harvard Law Review and before he set his sights on the presidency, has been mined for evidence that he was a youthful cocaine user.
With her statuesque looks, working-class roots and Harvard law education, Michelle cuts a formidable figure.
But she put her foot in it by saying after one primary: "For the first time in my adult lifetime, I am really proud of my country."
... and his Republican rival
Born in the Panama Canal zone, McCain was a temperamental handful from the outset: "At the smallest provocation, I would go off in a mad frenzy, and then suddenly crash to the floor unconscious," he admits. His father and grandfather were both highly decorated admirals. McCain was subjected to torture during the five and a half years he was held by the Vietnamese after being shot down, but gave them as good as he got.
McCain is running his campaign on a relative shoestring. He turned this to his advantage early on but he needs a vast amount of money for the presidential campaign ahead. He asked President Bush to raise some cash for him last week. McCain has little more personal wealth than he did 20 years ago but his wife is worth $100m.
Behind McCain's pancake make-up are traces of an ugly scar from the head and neck surgery he needed for skin cancer in 2000. Last week, doctors said the 71-year old was in excellent health. But he suffers from kidney stones (which may account for his temper tantrums) and takes medication for high cholesterol. Wounds from the Vietnam War mean he is incapable of raising his right hand above his shoulder – so cannot brush his own hair.
McCain is hot stuff at the barbecue. His seasoning of choice is Hog's Breath – a mix of salt, pepper, garlic and paprika. He once joked that, if he became president, he'd replace Bill Clinton's White House putting green with a grill.
The pride of the McCain family menagerie is a 25-inch iguana which lives in a glass case. Then there is the hamster and Leo the snake.
Under a McCain presidency, super-wealthy Americans might benefit from an attempt to make George Bush's tax cuts permanent. McCain defines his mission as "reforming and reinventing government", by which he means slimming it down. He is hostile to the sort of government agencies that led to the disastrously slow response to Hurricane Katrina and the housing market collapse.
McCain tends to confuse his Sunni with his Shia and for a foreign policy expert manages to keep putting his foot in it on big issues. But for some reason the mainstream media always give him a free pass. TV anchors get all emotional talking about his Vietnam War years.
The staple McCain campaign diet was Dunkin' Donuts, pizza and bourbon. He was once matched drink for drink by Hillary Clinton on a night flight to Iraq.
McCain is already beating the drums of war and warning Americans that a nuclear-armed Iran would threaten Israel and withdrawing troops from Iraq would weaken the entire Middle East. He is trying to tar Obama as soft on terrorism, pointing out that Hamas has endorsed him for the White House. Americans are weary of the never-ending "war on terror" but another al-Qa'ida attack, or even the threat of one before November, could send "security mom" voters back to the Republicans.
If McCain wins the White House, some will attribute victory to the Spring Hill Lizard – which isn't really a lizard, but a spell cast by wiggling his right little finger. McCain always carries his lucky compass, lucky feather, lucky penny and, at times, a lucky rock.
Hardly a week seems to go by without another skeleton clattering out of McCain's cupboard. If it's not a senior member of his staff being sacked for ties to lobbyists, it's about his wife Cindy's investments in companies operating in Sudan or the "sweetheart deals" he arranged for developers. He was endorsed by the televangelist John Hagee, who says the Catholic Church is "the Great Whore", but they have since parted company.
McCain, who is no God botherer, needs to persuade distrustful Christian conservatives that he is with them on abortion and creationism. He told them a heartwarming story from Vietnam when a prison guard loosened his bonds after he made a cross in the dirt. Nice try.
McCain has published a handful of books, the best of which is his New York Times best-seller Faith Of My Fathers. It is a good read (co-written by his aide Mark Salter) and tells the compelling story of the torture he suffered in Vietnam and his hell-raising days as a Navy flyer.
As a fighter pilot McCain scandalised colleagues with his exotic-dancer girlfriend. He divorced his first wife on his return from war, hooking up with Cindy, left – 18 years his junior and heiress to a beer fortune – who overcame an addiction to prescription drugs.
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