Leading Article: Ashdown in action makes the case for change

"Mummy, what is that man for?" If we apply the classic test to Paddy Ashdown, the answer has to be that his purpose is to open up the possibilities of British politics. It is too simple to say, as many Labour politicians do, that the Liberal Democrats enjoy the luxury of being able to adopt positions which are only capable of winning minority support. This assumes that the way to win elections is, like a boxer, to get ahead on points and then bury your head in your opponent's chest so that he cannot hit you. Tony Blair assumes that any party seriously aspiring to win a majority of seats in the House of Commons cannot, for example, advocate higher taxes to pay for better public services. If it were not for the Liberal Democrats, the middle ground of politics would be defined by a conspiracy between the two largest parties, and the election campaign would be even more stifling than it has been.

The Liberal Democrats have stretched the envelope of public debate. It may be that Labour has been forced into its hedgehog position on tax only because of its past history, and voters' distrust of it. It may be that a different tax policy could win the assent of a majority if it came from a different party. And some aspects of the Liberal Democrats' policy are commendable. There are in fact two elements. One of simple redistribution: higher income tax on those earning more than pounds 100,000 to cut tax for those on lower earnings. And one of honesty about public finances: higher income tax generally to pay for increased spending on education.

Using the tax system modestly to close the gap between the better-off and the poor would have been a long-overdue token of a new public ethic. And, although a penny on the standard rate of income tax is far from the best way to raise it, the Liberal Democrats are to be praised for their directness in saying that better public services have to be paid for - something Mr Blair, head down, gloves up to his face, cannot say, despite the words "Education, education, education" stitched on his banner. Mr Ashdown makes the same point ("5p on a packet of fags") in relation to the National Health Service, which, as The Independent has reported in recent days, does not meet our aspirations for it, despite hugely increased real resources over the past 18 years.

Mr Blair may be right that Labour cannot win as a tax-and-spend party, but his argument is logically flawed: just because Middle Income Britain has "suffered enough" from tax rises does not mean it is wrong to put taxes up more. At least, because of Mr Ashdown, Mr Blair has been forced to try to justify himself.

In some ways, of the three national party leaders, Mr Ashdown has had the best campaign - certainly the most enjoyable one. Realistically, he will not be prime minister on Friday. So his role is not to play at being prime minister, but to act out the possibilities which could be encompassed by a candidate prime minister. Occasionally, the necessary pretence that he could form a government has slipped. Mr Ashdown has been teased by The Independent's Anthony Bevins for not knowing what was in his 1992 manifesto and by Newsnight's Michael Crick for not running a campaign in Meriden, which he needs to win for a Lib Dem majority in the Commons. But it has been a good performance. He has argued with passion and clarity that every single Liberal Democrat vote will count as a vote for more resources for education and health.

Interestingly, what he has not said with anything like the same force is that every Lib Dem vote will dramatise the case for a fairer electoral system. Perhaps this is because he recognises that electoral reform is not a vote-winner. Perhaps it is because he fears that if Mr Blair is pushed on the issue, he would take an even more negative stance than simply being "not persuaded" of the case for electoral reform. Either way, it remains one of the most compelling reasons for voting Liberal Democrat. Every additional vote for Mr Ashdown's party piles on the pressure to persuade Mr Blair that the present system disfigures our democracy, and to hold a Labour government to its pledge to consult the people in a referendum before the next general election.

Like the pledges on education and health spending, this fact also tends to appeal to anti-Conservative tactical voters. Thus Mr Ashdown has extracted every possible drop of advantage from what seemed three years ago to be an unpromising strategic position. When Mr Blair came to the Labour leadership, one of the first things he did was to launch an all-out assault on Lib Dem territory, including laying claim to the Liberal tradition of Keynes and Beveridge. For a moment it looked as if the Liberal Democrats would not survive the boxer's bear-hug. But Mr Ashdown's repositioning of his party has worked - he ended "equidistance" and robustly asserted a form of social democracy which now lies well to the left of New Labour.

This has produced a bizarre situation where most Labour Party members find their core beliefs publicly reflected better by the Lib Dems than by their own leadership. This seems to have done nothing to prevent disaffected Tories switching to the Lib Dems, while leaving Mr Ashdown's party poised to benefit from tactical voting from Labour supporters. Indeed, it is possible that the Liberal Democrats could sweep from their Celtic fastnesses across almost the entire West Country.

It may be that what we will see on Thursday in the rest of the country will be a shallow Labour landslide, in which Mr Blair wins a substantial parliamentary mandate on a negative, anti-Tory and unenthusiastic vote. If that is the case, then the case is even stronger for as many Liberal Democrat MPs as possible to be elected, to stiffen the progressive resolve of a Blair government.