Leading article: Great opportunities are open to the Liberal Democrats

Nick Clegg must explain what is distinctive about his party's policies

There's nothing like the hint of power to boost a party's popularity. With the opinion polls pointing to the possibility of a hung parliament, the Liberal Democrats are being unsubtly wooed by both the Labour and Conservative leaderships. This attention is already raising the profile of the third largest party and its leader, Nick Clegg.

And with the personable Mr Clegg also set to benefit from the publicity that will flow from the new television debates between the three leaders (more even than either David Cameron or Gordon Brown) a healthy wind appears to be filling Liberal Democrat sails.

It is often said that the third force in British politics lacks a clear "selling point" of the sort they had in the 2005 election on Iraq. This new spike in exposure is thus a golden opportunity for Mr Clegg to tell the public what is distinctive about the Liberal Democrats in their attitude to Europe, the voting system, civil liberties, the environment and on securing economic recovery.

There are dangers too, of course. Labour and the Tories would dearly love to smother the third party to death through affection. If the electorate see Mr Clegg leaning to either Labour or the Tories, the pernicious old accusation that a Liberal Democrat vote is a waste could easily resurface.

The good news for the third party is that Mr Clegg's stance on any future deals – that it is the British people, not he, who will be the "kingmaker" – is solid. This gives the Liberal Democrats clear distance from their rivals, but without diminishing their newfound relevance.

Yet there is another, less obvious, danger. In the past, the Liberal Democrats have been able to get away with fuzzier policies in election campaigns than the two larger parties. Their perceived distance from power meant that the spotlight of media scrutiny often missed them. That will not be the case this time around.

On the economy the Liberals have a relatively coherent message: to tax housing wealth to pay for reductions in income tax for the lowest paid. They also propose reductions in public spending and a freeze in most civil service salaries in order to bring down the deficit. This amounts to dealing with the fiscal crisis in a radical but socially fair manner.

But on matters of tax and spend, the devil is always in the detail. The Liberal Democrat Treasury spokesman, Vince Cable, has been more candid on which programmes he would cut than his counterparts in other parties, advocating scrapping Trident and university participation targets. But the Liberal Democrats still have some expensive spending commitments, such as phasing out tuition fees and reductions in class sizes. Anything they announce on tax and spend has to be able to withstand rigorous public scrutiny.

And they certainly need to learn from their mistakes. The party was embarrassed at its conference last year over the mansion tax, when it turned out that senior frontbenchers had not been properly briefed on the new policy. And the entire programme was revised shortly after. The Liberal Democrats just about got away with that shambles. But any more sloppy, back-of-an-envelope style policies could prove fatal to the party's credibility.

Great opportunities and great dangers lie ahead for the Liberal Democrats. The time for Mr Clegg and his party to prove their seriousness of intent has arrived.