As politics has become more of a job for life, it's also become more of a science and less of an art, as parties have made more use of sample-based polling and the techniques of marketing, including sophisticated advertising and focus groups. There was a time when politicians relied on their own contact with voters and their gut feelings to assess how their policies and performance were being received by the electorate. These days, their polling and reports of focus group discussions leave them in no doubt about what voters are thinking on all topics. Or, at least, leave them imagining there's no doubt. In truth, even quantitative polling can be misunderstood and qualitative research from focus groups is so subjective it's notorious for the bum steers it can give. Even so, it does seem the parties get very similar messages from their rival efforts.

When focus groups were introduced, the rationale was they would inform the parties on how to frame the policies they wanted to pursue in ways that made them more attractive to voters. But when you are – or imagine yourself to be – fully informed on what the punters like and dislike, the temptation to let those preferences determine what policies you pursue must be almost irresistible. What this seemingly less amateur and more scientific approach to politicking overlooks is the often paradoxical quality of human nature. Tell me only what I want to hear and I begin to wonder whether I can trust you. What exactly do you believe? Keep it wishy-washy and I wonder if you really believe anything.

Only ever tell me nice stuff and I wonder whether you're tough enough for the job. Become a slave of focus group approval and you risk forgetting that, though I don't like the sound of your plan, I could be persuaded it's what the country needs. In the old days, a politician like Fraser won elections because he was seen as a stern father the times called for, not because he was popular. Another drawback of the more calculated approach to politics is governments' ever-increasing superficiality. If, as all politicians believe, "the perception is the reality", why not focus on perceptions and appearances and let reality slide?

If the trains aren't running on time or people are waiting too long for elective surgery, why not measure these things in ways that are more favourable? Why not favour responses to problems that are flashy or emotionally gratifying rather than boring but effective? Why waste scarce resources on repairs and maintenance or renovation when you can build something new and be seen cutting the ribbon and making great progress? When the number of problems or worthy causes far exceeds the revenue you've got to spend, why concentrate on those where your spending is likely to be most effective rather than slinging an inadequate sum to as many as possible and so mollify as many potential critics as possible? Why give much to people such as the unemployed or single mothers for whom there's so little public sympathy?

When the public takes an irrational set against outsiders such as boat people, why not gratify their prejudices rather than defend the needy? When people convinced themselves they're struggling to keep up with the cost of living but the objective indicators say wages are rising faster than prices, why try to set them straight when it's so much easier to pretend to be sympathetic? In short, why not reinforce prejudices and misperceptions rather than educate? Why not follow the voters rather than lead them? "There go the people. I must follow them for I am their leader." When memories and political terms are so short and punters so ungrateful, why not be short-sighted and risk averse?

All those temptations are reinforced by the media. It's the media that are overly preoccupied with and impressed by the new rather than the old, by the flashy and the emotionally gratifying, by what's on the surface rather than what's underneath, by the immediate rather than the prospective, by the irrational rather than the rational, by the sympathy-rousing case study rather than the systemic failure. Politics has changed over the years but so, too, have the media. And they've both changed in ways that are mutually supportive. The two institutions have become more symbiotic. There's no doubt the speeding up of the 24-hour news cycle is essentially the product of the media's ever-shortening attention span as part of the intensifying competition between the media's ever-proliferating mediums, including the advent of 24-hour news radio and TV channels. But a lot of the dumbing down has been initiated by the politicians and their party machines for their own reasons. There is plenty of blame to be shared between the two institutions. This edited extract from Gittins by Ross Gittins, published by Allen & Unwin, is out this week.