Rosenstock, as many of you will know, is the man behind Gift Grub, Today FM's phenomenally successful sketch segment, which can be heard twice a day most days during Ian Dempsey's breakfast show, and which has spawned a series of bestselling albums. It can be side-splittingly funny, if you'll excuse the lame attempt to be quoted on the next album sleeve. Rosenstock's impressions are top-notch, and he adds to his list of victims all the time. Tommy Tiernan was recently nominated as Ireland's funniest person but, for his ability to engineer smiles and laughs at an hour of the morning when few enough of us are in great form, or in any form at all, Rosenstock would get my vote.

However, he is more of a caricaturist than a satirist, which can be a problem when he enters the political arena. Satire, when done well, is almost always cutting and diminishing, seeking to undermine or damage the reputation of the person being satirised.

Ideally, it will be done humorously, lest it degenerate into pure personal attack.

Caricature can be either positive or negative, exploiting somebody's physical, psychological and emotional tics and idiosyncrasies to generate a laugh or a smile, or, alternatively, to portray the person as sinister in some way. Any caricature of the singer Barry Manilow, for example, will make great use of his unfeasibly large nose. Most of the time, there is no malice intended.

In caricatures of Jewish people over the years, however, noses . . .

hooked, pointed, long . . . have been used to maintain a stereotype of Jews as shifty, menacing and untrustworthy.

Rosenstock's caricature of the Taoiseach is uniformly positive and contributes hugely to Ahern's carefully crafted image of himself as an ordinary Joe, somebody who is on the side of the common man and woman, impatient with the demands of the fools who surround him. The Gift Grub Bertie is regularly to be heard saying "Ah Jaysus", as his desire to be left alone to behave in a normal manner is undermined by the crazy demands of the world he lives in. In that respect, he could be you or I. The worst you could say about the Bertie Ahern portrayed on Gift Grub is that he is a bit of an innocent abroad, desperate to maintain the ordinariness that has served him so well, but in desperation because he is constantly being thwarted in his quest to live such a life.

During the last general election campaign, when satire would have been very welcome, Gift Grub essentially acted as an unpaid public relations agent for the Taoiseach. Whereas Rosenstock's Ahern was his usual put-upon self, the then Fine Gael leader Michael Noonan was caricatured as a metaphor-obsessed windbag. He was a sneer, a compulsive ironist, a bit nasty. The warmth that attached to the portrayal of Ahern was completely absent in the caricature of Noonan.

I'm not for one minute suggesting that Gift Grub won the election for Fianna Fail, but Today FM's breakfast show had an aggregate weekly listenership of about one million people at the time . . . it has even more listeners now . . . so it would be equally stupid to suggest that those listeners who bothered to vote weren't at least a little influenced in their decision by three or four weeks laughing out loud at the differences between cuddly Bertie and nasty Noonan.

In this newspaper last weekend, Rosenstock was one of a number of people interviewed about the Taoiseach's 'x-factor', that Teflon quality which allowed Ahern to emerge from one of the dodgiest group of politicians ever to blight this country and go from one electoral success to another. My own, not particularly original view is that along with Charles Haughey (whose corruption he blithely facilitated), Ray Burke, Padraig Flynn and others, Ahern lowered public expectations of Irish politicians and politics to such a degree that as long as he isn't caught in the act of committing a crime, people will look fondly on him.

In his Sunday Tribune interview, Rosenstock fell back on the "man of the people" theory about Ahern's popularity. "I think one of the reasons why Bertie is so popular is that he is able to identify himself with the common people of Dublin and Ireland, " he said. "People have responded well to our Paddy the Plasterer sketches over the last few weeks and our song about him was received well. People complain about the lack of satire in Ireland, so I think our Bertie sketches respond to that. In light of the current controversy, most people realise that he is not Charlie Haughey and I don't think that it is the case that he has been feathering his own nest. Perhaps he hasn't done anything wrong."

Perhaps, perhaps, perhaps. As we are only about 200 days away from a general election, and in light of the fact that RTE has long ago abandoned any efforts at political humour lest it offend somebody, Gift Grub will be the nearest thing we get to satire on the national airwaves in the runup to the poll. It is a little worrying, therefore, that the only vaguely satirical portrayal of the Taoiseach between now and next spring will be done by somebody who is clearly very fond of him, has bought into the "man of the people" myth, and believes that indiscriminately accepting payments from businessmen is a definition of doing nothing wrong.

One awaits with interest Gift Grub's take on Enda Kenny, a character with which it is still grappling. If Kenny is presented with the same warmth and affection as Ahern, then no great harm will be done. But if Kenny is portrayed as negatively as Michael Noonan was last time around, Mario Rosenstock and Today FM will stand accused of deliberate bias. It's worth keeping an eye on.