KEY POINTS:
They have already been on the best-dressed - and worst-dressed - celebrity lists.
Profiles of each have been written in all the key news magazines and their backgrounds and parentage thoroughly scrutinised.
As their husbands search for vice-presidential candidates, Michelle Obama and Cindy McCain are readying themselves for the strange supporting-role approval contest that comes with being America's First Lady.
The term itself may be anachronistic - Jacqueline Kennedy said she dreaded becoming one: "It sounds like a saddle horse."
There is no official job description, though puritan values and good housekeeping are unspoken expectations.
But for Cindy and Michelle, both clever and successful, and both mothers, this political showbusiness means very different things.
Two weeks ago the heiress Mrs McCain, 54, was in Coronado, San Diego, sorting out the beachfront apartment she and her 71-year-old husband have just bought. Mrs Obama was on the campaign trail with her husband, getting a foretaste of the nasty attacks she can expect now he's won the nomination after Tuesday's final Democratic party primary polling in South Dakota and Montana.
With race the subtext, conservative radio jocks and bloggers have been growing more strident, depicting her, as one US commentator did, as "the bitter, anti-American, ungrateful, rude, crude, ghetto, angry Michelle Obama". This vehemence has provoked Barack Obama to call the attacks on his wife, from people purportedly promoting family values, "detestable".
Cindy has already been here. The only child of a wealthy Arizona beer distributor, she was targeted by proxies for George W Bush, then Texas governor, during her husband's first presidential campaign in 2000, who leaked news of her past addiction to painkillers and, inaccurately, of her husband's alleged black love child (the couple have a daughter adopted from Bangladesh).
In one sense, the two candidates for First Lady could hardly be more different: Michelle Obama, black lawyer, Princeton and Harvard educated, raised in a tiny Chicago flat; Cindy McCain, highly strung, bottle blonde second wife, a former rodeo queen from a privileged family in the white state of Arizona.
If they have anything in common it is their fiercely guarded priorities - their children come first. Michelle's time spent on the campaign trail is determined by her getting back to her girls by bedtime whilst Cindy considered asking her husband to quit politics when their daughter Bridget was hurt by political slanging.
Both have the same role between now and the vote in November: attractive co-stars there to mollify Hillary Clinton supporters disenchanted by what they see as misogny underlying her campaign experience.
Whoever will carry the White House keys in their tastefully chosen handbag, both seem likely to refashion the First Lady position, seeking neither the over-reaching ambitions of Hillary Clinton during her husband's first term, nor the understated lady of the manor approach of Laura Bush.
"The job description is up for grabs," says Sally Quinn, author, hostess, and wife of former Washington Post editor Ben Bradlee.
"Cindy McCain would be a more traditional First Lady. She has her aid programmes in Africa, but she's not particularly interested in the limelight, has done very little campaigning for her husband and doesn't talk a lot. Even though she's not that much older than Michelle Obama, she could be from another generation."
Michelle Obama, believes Quinn, would be a more proactive presidential spouse.
"She'll take on serious projects, but she's not like Hillary Clinton's buy-one, get-one-free deal. She does not want to be co-President.
"She is the mother of two young girls, so that will be her first priority, but she's also a brilliant lawyer."
Michelle recently suggested that if she became First Lady, she would take on women's and family issues she has heard on the campaign trail. "I want to ensure that their voices don't get drowned out ever again."
She presents a formidable character, strategists fear too much so for voters. Asked earlier this year if she could support Clinton if she got the nomination, Michelle said with undiplomatic realism: "I'd have to think about policies, her approach, her tone ..."
She is honest, and frankly diminishes her husband's mystique with comments about his bad breath, big ears, domestic failings (he doesn't put the butter away) - or saying he's not the "next Messiah" but "he's just a man".
If Obama wins in November, Michelle would not only be the first black First Lady but also, at 44, one of the youngest since Jackie Kennedy.
"Michelle is clear that Obama would be President," said Quinn. "She would be his wife, but have a direction of her own."
Cindy McCain's supporters say her blond hair and impeccable Stepford Wife appearance mask an earthy fortitude. She and her husband live apart (she in Arizona; he in Washington) but whether she's negotiating to clear Angolan minefields, or planning trips to highlight mass killings in Darfur, she is committed to her philanthropy and drawn, like her fighter pilot husband, to intensity.
"It's not about being a cowboy, I don't want anyone to think that's what I do," she said recently. "It's just these types of things don't necessarily happen in Phoenix, Arizona, and you have to go where it is."
Cindy suffered a stroke in 2004 and has made no secret of her misgivings over her husband's decision to run a second time. "This isn't her dream," said Quinn.
When John McCain suggested a second run in 2006, his wife ignored it and half hoped the idea would go away. "Life was good, I was alive from the stroke, and I thought, 'My gosh, let's just enjoy life a little bit'," she said. With two sons in the military, her husband told her, it was something "he wanted to do badly".
Yet she remains committed to her privacy. A profile in American Vogue last month elicited little new information except that she wears size-0 Lucky jeans, tried to cure her "emptying nest" problem by buying two Yorkshire terriers; and laments that she'll be limited to American fashion if she becomes the First Lady.
If she seems remote and steely - she refused to release her tax returns until pressured to - it's because she often is. At rallies, she says she's often thinking about things she has to do, or is looking out for trouble. "I'm looking at the faces and sometimes I'm spotting troublesome spots."
For the two leading candidates' wives, the White House offers much scope to pursue their causes even if tradition dictates they must be seen to be arranging Thanksgiving dinners, bedecking the Christmas tree and reading fairytales to visiting children.
Despite the importance of being seen to be conventional, the role of First Lady is not fixed. "You can make it anything you want," said Quinn.
CINDY LOU HENSLEY MCCAIN
Born: May 1954 in Phoenix, to one of Arizona's richest families.
Married: John McCain in 1980, a month after his divorce from first wife Carol. An heiress, she had a pre-nup to preserve her family assets and partly funded his bid for Congress.
Educated: University of Southern California _ masters in special education.
Salary: $6m in 2006, estimated worth $100m.
Work: Chair of Hensley & Co, a huge US beer distributors. Philanthropist, on the boards of several charities.
Children: Meghan, 24, Jack, 22, Jimmy, 20, and Bridget, 17.
What Cindy has to do: Be less defensive about her money and play down her marital age gap. Smiling more wouldn't hurt.
Verdict: Formidable but flawed.
MICHELLE LAVAUGHN ROBINSON OBAMA
Born: January 1964. Raised in Chicago in a one-bedroom flat.
Married: Barack Obama October 1992.
Educated: Princeton and Harvard law schools.
Salary: Earned $273,618 in 2006.
Work: Vice-president of external affairs at University of Chicago hospitals. Sits on six medical and academic boards.
Children: Malia, 9 and Natasha, 6.
What she'd have to dump as First Lady: Sarcasm.
Verdict: Driven and outspoken.
- OBSERVER
