Five years later, the sweet taste of power has soured

Get stuck in, Nick. Take no prisoners, Vince. Give the Tories and Labour a few home truths, Danny. No one would be falling out over expansion schemes for airports. Instead, the Liberal Democrats would be enjoying the pleasures of another bounce in the opinion polls. In 2009, after Bournemouth, YouGov estimated their support at an impressive 23 per cent.

In Glasgow, Nick Clegg and his party can only dream of such heights. Even a double-digit rating is the stuff of history. In England, Ukip have left them in the dust and the Greens are breathing on their necks. For loyalists, a taste of government no longer seems sweet. That 2009 conference slogan - "A Fresh Start for Britain" - has acquired an unanticipated meaning.

In one sense, it's old news. Mr Clegg has certainly mastered the knack of brushing aside each and every opinion poll. He is naught but our martyred servant, bearing the slings and arrows for the greater economic good. Should voters choose to disdain his sacrifice, he will just have to stiffen his lip again and soldier on. But in which direction?

Mr Clegg and his party have presented a spectacle in Glasgow this week that is, frankly, bizarre. Speaker after speaker, ministers above all, have excoriated the Tories as dangerous, deceitful fanatics before sprinkling a bit of ordure over Labour. Vince Cable has called George Osborne a liar - for who else could he have meant? - for pretending that tax increases are avoidable after 2015. All the while, an elephant has gambolled around the SECC.

With whom are LibDems in coalition? Whose offer of coalition would the party's elite refuse next May? The fanciful notion that Mr Clegg, Mr Cable and the rest have "restrained" the Tories these four years past gets its answer in those decisive opinion poll ratings. The public, with hordes of former LibDem voters in its ranks, recognises enablers. A few insults aimed at David Cameron or the Chancellor for the sake of "differentiation" won't alter the fact.

Despite it all, so it is reported, the conference mood is "upbeat", even chipper. As our Kate Devlin explained on Radio Four's Today programme yesterday morning, authentic LibDem rebels quit the party long ago, but that still leaves a mystery. What do the remainder hope to achieve? Acting as the whipping boys and girls for the Tories has induced only a profound contempt among all but handfuls - 8 per cent, says the latest YouGov - of voters. Providing the same service for Labour would produce the same reward.

The leadership clings to the fact that many LibDem MPs ought to be hard to shift, at least in theory. The strategy, such as it is, is to fight the next General Election as a series of by-elections. Mr Clegg's party is betting its life on a first-past-the-post system it has condemned for decades, but you won't hear much about that inconvenient truth in the months to come. Nevertheless, despite any comfort they might take, at least a couple of dozen MPs (from 56) have good reason to worry.

It's not, not in a proper sense, their problem. What remains of a party when its only remaining function is to keep a handful of people in ministerial office? Grassroots activism was once the LibDems' pride and boast, even - as some used to argue - its real purpose. Its rivals acknowledged that the party had a talent for that kind of politics. But how local can you hope to be with 8 per cent support while running the risk of being outstripped, in share of the vote, by Ukip?

For long years, LibDem activists have been fed the line given to all the dedicated foot soldiers of party politics. What point is idealism without power? What use is all the work and all the argument if a party cannot "make a difference"? If Mr Clegg's party still contains people with any grip on reality, they know the answer now. Their movement has been destroyed for the sake of a few careers and, above all, a Tory government.

Why was a confidence and supply deal unthinkable in 2010? Why would it be impossible in 2015, in a hung Westminster Parliament, for anyone holding the balance of power to restrict support to motions of confidence and money, or at worst pledge to abstain? The LibDem elite would no doubt produce a lot of sonorous rhetoric about instability and the need to steer the economy through endlessly choppy waters. The proper answer to those problems is a fresh election.

Mr Clegg has performed one service. He and his colleagues have shown that coalition government, under first past the post system, is the least satisfactory - and least democratic - carve-up available. After all, one fact is too often forgotten about the deal the Deputy Prime Minister still defends. In 2010, no one voted for it. In fact, a great many now-disgruntled people voted LibDem to "keep the Tories out", at his urging.

These Conservatives, it transpires, are terrible people, people who are not be trusted for an instant unless you happen to be - says Mr Cable - a "dodgy billionaire". No doubt those very thoughts were going through the Business Secretary's head when he sold off Royal Mail for £1 billion less than it was worth to New York hedge funds and other iffy types.

Did those tyrannical Tories force his hand? Or is there a difference between what a minister tells conference and what he does in the day job?

It is for the remaining LibDem faithful to forgive and forget. Most voters, say those opinion polls, don't succumb to amnesia so easily. They are not fooled by a party leadership that is once again setting out its stall for coalition, once again proposing to offer a restraining hand while the two larger factions in the Westminster tripartite alliance survey a changed landscape.

Labour is beginning to pay the price for Ed Miliband's inept leadership. The Tories are ahead in a couple of polls for the first time since 2010. Thanks to Ukip in England, neither party is in a happy place. Thanks to Scotland's referendum and his own destroyed credibility, the Westminster balance of power might not Mr Clegg's toy for much longer.

LibDem ministers need voters to believe that their role in government is worth preserving. There is no sign that the electorate has any such belief. If Mr Clegg and his colleagues hope shocking tales of Tory perfidy will do the trick now, four years on, they insult anyone entitled to cast a ballot. But they also demonstrate just how irrelevant they have been since 2010.

"Don't blame us; blame the people we've kept in government all this time"? That's quite a slogan.

And Mr Miliband will be the first to say he'll have no truck with those LibDem remnants, won't he?