By Nick Assinder BBC News Online political correspondent

Kennedy goes down well with voters

His critics are all too ready to suggest it is frivolity, a lack of "bottom" as they love to say in Westminster.

His real enemies - often from within - will even go so far as to whisper that it is an accurate reflection of his love of the good life.

CHARLES KENNEDY Born: 25 November 1959 Elected: 1983 as MP for Ross, Cromarty and Skye (now Ross, Skye and Inverness West) Leadership: Succeeded Paddy Ashdown as Liberal Democrat leader in 1999 High: Helping his party to make gains in the 2001 general election, prompting talk of the Lib Dems as growing opposition force. Low: Questions about his commitment to the role of leader surfaced last year.

His supporters see that as either the typically po faced attitude of those who believe politicians should always walk around with faces like wet weekends - or part of the campaign by would-be leaders and others to destabilise him.

For the punters, of course, it seems to work wonders.

Hard slog

It shows he is not only a real person but that he is actually a rather interesting person with, heaven forbid, a sense of humour and a life.

His appearances on programmes such as "Have I Got News for You" are mocked by the po face brigade.

But they have ensured he is recognised in the street, something few politicians, let alone Lib Dems can claim.

And, needless to say, the caricature is just that.

The idea that he doesn't put in the hard slog, for example, was comprehensively blown apart by his performance in the last general election campaign.

Lib Dems stood against war

He hit the road running, or more accurately flying, and while the other leaders were still getting up to speed he had already visited just about every constituency in Britain in one afternoon.

And his approachable, self-deprecating style won him more friends, leading to one of the best ever performances for his party.

Good bloke

Mr Kennedy has been a career politician since his triumph in capturing a seat for the SDP aged 23 in 1983.

He became leader of the Liberal Democrats in 1999 after building a reputation as a high-flier in his party, including four years as president.

Since becoming leader, he has managed to carve out some distinct policies for the Lib Dems, most notably on taxation, while still just about avoiding the charge that the party is more left wing than the government.

And most recently he struck a chord with voters with his anti-war stance.

But does any of this amount to anything other than the fact that the third party has a good bloke leading it?

The Lib Dems - or their Liberal or Alliance predecessors - have apparently been on the verge of the big breakthrough more times than Arnold Schwarzenegger has "been back".

Former leader David Steel infamously told his 1981 party conference to "go out and prepare for government".

And Mr Kennedy's action man predecessor Paddy Ashdown did a deal with New Labour that nearly put him in the post-1997 cabinet.

And at last year's conference, Mr Kennedy predicted the next general election fight would be between his party and Labour.

Fed up

But can he really pull off what none of his predecessors have managed?

The third party is caught in a classic catch 22. People don't vote for them in large enough numbers to elect them because they don't think people will vote for them in large enough numbers to elect them.

It is the dilemma every third party leader has faced.

Thanks to growing disillusion with New Labour and a flatlining Tory party, things do look better than usual for the Lib Dems.

And the Brent East by-election result emphasises that to a huge degree.

Mr Kennedy's task is to capitalise on that and persuade those fed up voters that he is not just a good bloke, but a potential prime minister.