What's become clear over this election is the sheer futility of political interviewing today: rather like bacteria that have developed resistance to antibiotics, politicians have become immune to interviewers' techniques. Peter Mandelson offered a fine demonstration of the new indifference on David Starkey's show on Talk Radio on Sunday, combating Dr Starkey's gleefully partisan and intellectually engaged jabs and scurries with a display of weary good manners - "If you'll allow me to finish... please let me answer the question you've asked..." - which bore little relation to the actual pattern of the conversation.

Phone-ins are supposed to get round this sort of thing. The theory behind the political phone-in is, I take it, that while politicians will feel free to ignore questions put to them by professional journalists, they can't do this to members of the public: here, at last, they will be on the spot. This idea is fuelled by the lovely memory of Mrs Thatcher squirming as a housewife interrogated her over the sinking of the "Belgrano". Sadly, though, it no longer works. The most skilfully evasive exchange of the election so far came when Gary from London called Dr Starkey to ask Peter Mandelson what had happened to the word "socialist", which he couldn't track down in Labour's manifesto. Well, Mr Mandelson replied, all Labour's values underpinned the manifesto. The conversation continued:

Gary: But are they socialist values?

PM: You can apply whatever label you like, what's important is that, at root, we have certain core beliefs and certain values which have driven us throughout our achievements throughout this century and will continue to do so as we go into the next.

Gary: And those core values have always been socialist. Are they socialist now?

PM: If I didn't subscribe to these values, Gary, I wouldn't be in the Labour Party.

Gary: Well, it's not a difficult question, is it? Are you a socialist?

PM: I am a member of the Labour Party and I subscribe to the values and beliefs on which our party is founded. I am not interested in bandying around labels or name-calling.

Did you spot the deft way he inserted a "these" where we would have expected a "those" ("If I didn't subscribe to these values, Gary..."), thereby making it impossible to pin down exactly which values he was referring to?

In the end, though, this sort of virtuosity is counter-productive - you can tell he's just showing off. Michael Howard has a rather better technique, which he brought into play on last Monday's Election Call. Again, he failed to answer the precise point put - for instance, defending stoutly the government's policy on mandatory sentencing without actually mentioning the issue of diminution of judicial independence, which was what the caller had been cross about. But he prefaces the evasion with a few words of anxious regret: "I'm sorry you feel that way..."

Something odd has happened here, which has less to do with politics than with the way we think radio works. Politicians no longer address the person they are supposedly talking to; instead, their remarks are aimed past them, at some notional floating voter who might be listening in. Listening to most phone-ins at the moment is like being at a party, where the person you're trying to talk to is constantly looking over your shoulder to see who else has come into the room. No wonder so many people are heading off to find the drinks table.