The Liberal Democrats are getting stronger, but they are still a long way from power

Charles Kennedy ended the Liberal Democrats' conference with a speech that reflected the mood of his party throughout the week. His address was substantial and serious. There were few moments of humour and no attempt to excite his audience with slogans that lift a speech but do not mean very much once the words have been delivered. The speech was therefore a sign of a maturing leader in charge of a party that is also growing up politically.

Without getting absurdly hyperbolic Mr Kennedy argued that Britain now had a three-party political system and that the Liberal Democrats were now a party of power. He had considerable ammunition to back up his case, with his party running councils previously held with big majorities by either the Labour or Conservative parties. He could also point to recent by-election wins. The two bigger parties have good cause to be worried.

The most powerful and passionate section of Mr Kennedy's speech related to the war against Iraq. He referred to the leaked documents published in a newspaper last weekend suggesting that Mr Blair committed Britain to war a year before the conflict took place, and that regime change was the objective from the beginning. Mr Kennedy proclaimed his determination to hold Mr Blair to account in Parliament on this issue. In doing so he got the biggest cheer from the hall.

Leading Liberal Democrats are concerned that their opposition over Iraq overshadows other policies and will not be a huge asset in a general election campaign. They should be less restrained. Mr Blair's pre-war conduct raises issues about trust and judgement that will inevitably be a central theme at the next election. It is their opposition to the war that gives them and their leader an especially distinctive voice.

Most of Mr Kennedy's speech focused on his party's detailed policy agenda. The proposals are a significant improvement compared with the party's programme at the last election. No longer do the Liberal Democrats claim that huge increases in public spending can be financed by a small increase in basic rate of income tax. Most of their current policies have been carefully costed. Even so, their leaders from Mr Kennedy downward have looked uneasy when challenged by interviewers about some of their tax plans. Neither Labour nor Tory leaders would be allowed to get away with any signs of pre-election flakiness relating to tax. A more downbeat message from this conference is that if the Liberal Democrats seek to be a party of power, every single policy needs to be assessed for flaws or hidden costs between now and the election.

The broad success of the conference should not disguise the many other challenges facing Mr Kennedy and his party. Even their most optimistic supporters would not claim they are in a position to win the next election. Sympathetic voters are therefore faced with the prospect of supporting a party almost certainly doomed to opposition for some time to come. Until they are strong enough to win a general election they risk being the party of the protest vote, at least in general elections. Mr Kennedy's insistence that they are a party of power applies to parts of Britain, but it is arguable they were closer to joining a government when Tony Blair and Paddy Ashdown formed their unusual alliance.

The debates in the Labour Party and within the Government mirror some of those that took place this week in Bournemouth. In spite of the calamitous war against Iraq, the Liberal Democrats will struggle to convince large swaths of Labour voters to desert a party in power for one that aspires to power. Although the Conservatives fail to make headway, it is still possible they will gain a few seats at the next election rather than collapse entirely. The amount of political space for the Liberal Democrats is not as great as it sometimes seems. The serious tone of the conference and Mr Kennedy's speech suggest that the Liberal Democrats are becoming a formidable political force, but they are still a long way from securing power at Westminster.