If you want to know what a culture really thinks of women, you could do worse than to consider how it treats those who marry high-profile politicians. If they're not photogenic, they'll be lambasted for their ugliness; if they splash out on a good haircut and stylist, they'll be blasted for their profligacy. If they give up work to support their partner, they're criticised as a drudge; if they work full-time they'll be chided as unsupportive (and, most probably, accused of trading on their partner's name).

Who would be a political spouse? Well, as Hillary Clinton - probably the most prominent political wife of all time - gears up to win the Democratic presidential nomination, the trail she blazed is, surprisingly, being taken up by a whole new breed of women. Following Hill, we are entering the era of the political wife who hears all the criticism of herself and her actions - and goes ahead and acts anyway.

Take Cécilia Sarkozy. The French president's wife has never been one to pull her punches - in 2005, she had a rather public affair with an advertising executive, and before her husband's election she commented that "I don't see myself as a first lady. It bores me."

Just a few months into Nicolas Sarkozy's presidency, though, and she was flying off to Libya on a mission to free the "Benghazi Six" - a group of five Bulgarian nurses and one Palestinian doctor, who confessed, apparently under torture, that they had infected children in a Libyan hospital with HIV. Cécilia was, of course, accused of barging in on a sensitive diplomatic process in which she had no official role. She also, not incidentally, helped get the medics released and safely back to Bulgaria. There have since been suggestions that she might travel to Burma to enter talks about freeing Aung San Suu Kyi.

In the US, Michelle Obama has been an impressive presence on the campaign trail, winning over crowds while mock-chiding her husband for having big ears and being undomesticated. The New York Times columnist Maureen Dowd wrote, in an article that criticised Obama from start to finish, that this approach made her "wince a bit". Did Michelle go and cry in a corner? "If you're 23 and reading Maureen Dowd's article," she noted, "you could be crushed. If you're 43, it's sort of like, 'OK, well, she obviously doesn't know who I am, and she doesn't understand.'"

Then there's John Edwards's wife, Elizabeth - potentially his biggest asset. When the right-wing writer and "personality" Ann Coulter appeared on the US phone-in show Hardball a few weeks ago, having called Edwards a "faggot" and said that she hoped he would be "killed in a terrorist assassination plot", Elizabeth Edwards phoned in and took Coulter down with all the righteous fury of a mother bear.

As much of a trailblazer as Hillary has been our own Cherie Blair - can I be the only person who actually quite liked her by the time she and Tony pushed off? She'd committed a few sins, of course, reportedly accepting wads of cash for a charity speaking tour and hanging out with a convicted fraudster (not to mention Cliff Richard), but something about her lack of reserve was brilliant. When Cherie picked up the microphone and sang at an official event, I cheered inwardly, as I did each time she voiced another unguarded political opinion. She was outspoken, effervescent, uncowed. In fact, she travelled so far from the days of Tony's first term - when she acquired the nickname "the silent spouse" - that no one even remembers that earlier persona.

By the time she left No 10, Cherie seemed to have become that rarest of creatures, a woman who doesn't give a damn about criticism. Women are so used to being picked apart: the thighs of three-year-olds are pinched by grandmas who say, "She'll have to slim down if she's to snare a husband!" - that coping strategies kick in early. Called sluts, teases or bitches as teenagers, criticised for their looks, intelligence or pride, young women quickly learn to apologise, confidence melting into a sea of self-deprecation. Knowing that other people will put the boot in, women learn to put the boot in to themselves first - "You might hate me, but hey, look, I hate me, too!" - a defence strategy that is patently self-destructive, and therefore entirely useless.

So far, our new Prime Minister's wife, Sarah Brown, seems to be carving out her own path, staying well out of the limelight. Which is absolutely fair enough, so long as that's how she wants to play it (as I'm sure it is), rather than how she feels she must (as Cherie so obviously did at the start of Blair's time in office). I never thought I'd take advice from Nancy Reagan, but one piece of counsel she offered Arnold Schwarzenegger's wife, Maria Shriver, has stayed with me since I came across it a few years back.

"No matter what, you'll be criticised," Nancy said, "so do whatever you want to do." Advice that's as relevant to any modern woman as it is to the new breed of political spouse.

Kira Cochrane is women's editor of the Guardian