We have had "Worcester Woman", "Mondeo Man", the "Pebbledash People" and others. Every election seems to throw up its special group of voters on whom politicians focus their attention.
This year's, it seems, is to be the internet mums – those educated, middle-class women at home with their tiny children, for whom internet chat sites have supplanted coffee mornings as their primary means of staying in touch.
Tomorrow, David Cameron will spend an hour online answering questions put to him by users of the Mumsnet site. It will be his second guest appearance. The first worked out very well, because he appears to be equally at ease whether he is asked about policy or more personal matters such as his home life.
Gordon Brown, by contrast, does not handle personal questions comfortably, and endured days of ridicule after his Mumsnet experience, when he was unable to answer a question put to him a dozen times about what his favourite biscuit was.
David Cameron is unlikely to have the same difficulties as he is bombarded with questions ranging from the serious – whether child benefit should be means-tested, for instance – to the deeply trivial, such as whether he prefers oatcakes on their own or with cheese.
"That is Mumsnet to a T," its founder, Justine Roberts, said yesterday. "It can be very serious, and it can be very silly. From my perspective, it did not matter at all whether Gordon Brown answered the question about biscuits. I think the reason it got asked 12 times was that people were slightly frustrated that the answers they were given to other questions were a little bit by rote, and because it seemed to be the easiest question to answer."
After his roughing up over "Biscuit Gate" it might be thought that Gordon Brown would never enter a virtual chat room again, but on the contrary, at the end of the hour he seemed delighted by how it had gone.
It is one symptom of the great mystery confronting the people who are planning next year's election campaign, for any political party. They know that it will be the first British general election that could be won or lost on the web, just as Barack Obama's victory last year was due in a very large part to his internet-savvy team. What they have not yet worked out is how to use it.
One of Tony Blair's undeniable talents was that he could spot changes in the social weather and seize on a vote-winning formula to deal with them. In 1992, the Conservatives adroitly held on to the votes of the middle-income homeowners, the ones they called the "Pebbledash People".
In 1997, Blair and his team fought back by targeting "Mondeo man" – who owned property without being rich enough not to need to use state schools and the NHS – and "Worcester woman", who lived in town but outside the usual Labour strongholds.
One of Tony Blair's greatest successes was to persuade women, who had made up the bulk of the Tory vote, to switch in huge numbers to Labour. He did this partly through his own media-friendly personality, but also by being surrounded by more than 100 women Labour MPs. While Labour looked like the family-friendly party, the Conservatives, as their former chairman Theresa May memorably put it, were the "nasty party".
It is that image which David Cameron has worked assiduously to change, while Gordon Brown, who is 15 years older than Cameron, is plainly ill at ease in this era of personality politics. The contrast between their styles has helped to create an uncertainty about how the entity that used to be called "Worcester Woman" will cast her vote next time. Panic bells were sounding recently in the offices of the pro-Labour Fabian Society, when they received the findings of a YouGov poll which suggested that Labour had lost the female vote. Andrew Hawkins, from the polling company ComRes, thinks that has not happened yet. His company's findings show that in every social group, Labour is still less unpopular among women than among men. "Labour has lost the middle class, big time, but I don't think that's gender-specific," he said. "If anything, it's the Tories who have got to do more to get women's votes."
Deborah Mattinson, of the polling company Opinion Leader Research, who carry out much of the Government's polling, said: "The women's vote is up for grabs. The women who are using sites like Mumsnet are a small group of voters, but they are iconic and it pays for the politicians to be seen to be talking to them."
But the problem perplexing party strategists is how to reach them, other than through guest appearances by politicians, which can be done only occasionally. Private companies with household products to sell have puzzled over the same question, and have tried having their PR people sign up and join the conversations – but the reaction has not been what they hoped. For the people using the sites, having someone coming on to push a product or promote a political cause is like having a private conversation interrupted by a gatecrasher.
Robin Goad, research director of Experian Hitwise, which advises on internet marketing, and father of a four-month-old boy, said: "There is an important and growing market as I know from personal experience. Over the last 18 months we have seen a marked increase in the number of searches for pregnancy sites as well as forums like Mumsnet. Women are increasingly using the internet during pregnancy as well as afterwards.
"The politicians are right to see them as an important target audience, but they are tightly run forums. The way to influence may be to target the people who are influential within the forums, because you will always have people who have a lot of authority within any online community, and you can try to get them to act as your advocates."
Roberts thinks anyone who tries to infiltrate online sites to promote a political party will soon get found out. "There is a sort of etiquette and politicians and others do well to observe it," she said.
Female intuition: Mumsnet on politics
*I judge Gordon Brown on his appearance: not his looks per se, but the way he carries himself. He often looks ill at ease, which doesn't really inspire confidence.
*How is your health? I really, really don't want to vote for you and suddenly find David Miliband is running the country
*There's only one person who could make the Labour party even more unelectable than Gordy – Harriet Harman.
*One thing that has been annoying me: the constant hum that Smith "wasn't up to the job" of Home Secretary ... Is there any particular evidence that Smith wasn't up to the job, rather than simply implementing some crazy and unpopular policies?
*I'm oop north and I hate Blears. "Squirrel" is a good descriptive word, kind of ratty and shrill and nuts.
*You can't trust people who have worked their way up to power. People born to power (like, er, the Queen) and people who, like parents, have power thrust upon them are a different matter.