Will Labour live to regret their mockery of the Lib Dems?

Belittled, mocked and jeered – the Liberal Democrats were made to look like irrelevant upstarts on a day that should have been their big moment. Will Labour regret their cruelty?

The awkward atmosphere in the Commons chamber as Danny Alexander tried to outline his 'alternative fiscal path beyond 2016/17 was excruciating. It was like sitting in the cancer test waiting room and being told by a drunken interloper: 'You're all going to die.'

The interloper was Labour frontbencher Andrew Gwynne, for whose conduct the single word 'heckling' just doesn't cut it.

His yapping – and waving of his prop of choice, the red Budget book – made it virtually impossible to concentrate on the chief secretary to the Treasury. "Is this your Budget?" he asked. "This is your government's Budget? What about this? What's this?" He went on and on and on, at one stage virtually throwing a copy across to Alexander's despatch box.

It was disgraceful. But it was also baffling, because if Ed Miliband is to stand any chance of getting into No 10 it seems likely he will have rely on the Lib Dems – even if their numbers are reduced in the next parliament.

The central Liberal Democrat message is that they offer moderation: either softening the harsh ideological drive to cut the size of the state favoured by the Conservatives, or sharpening the sloppy fiscal discipline they think voters associate with Labour.

So it makes sense that today's exercise helps strengthen their essentially ambivalent centralist stance. To right-leaning liberals they remain staunch deficit supporters because they will vote through the Budget proper when it comes to a division. To left-leaning types they have today's civil-servant-backed manifesto for 'fairness' in the form of an efficient Treasury document that echoes Labour's approach.

But with Labour scorn at the Liberals so obvious and painful in the chamber today, the strategy seemed dubious at best. "What a farce," shadow chief secretary Chris Leslie declared. "It's too late for this – the Liberal Democrats have backed the Tories all the way."

Adam Afriyie, barely the only Conservative in the chamber, was equally scathing. "Today's duplicity is an absolute betrayal of the role they played in government," he said. Stewart Hosie, the SNP's deputy leader, suggested Alexander had only gone to the bother of trying to "pretend he's important" in order to save his seat in Scotland.

Just to be clear, then, everyone hates the Liberal Democrats. The only difference between yesterday and today was that not so many people could be bothered to make that view known.

Gwynne's monologue was embarrassingly audible because the chamber was so empty. You can understand why the Tories kept away, but Alexander's own party too? Only nine Lib Dem backbenchers had bothered to show up to hear the statement – presumably because the rest of them were engaged in campaigning to save their seats.

Today's papers presented to parliament were unprecedented – a "constitutional innovation", as Alexander put it, that comes with the territory of coalitions. Its frosty reception just goes to show how unfamiliar real coalition politics is, even to Westminster types. The Liberals have stuck so closely to their Conservative colleagues' tunes that the idea that they would offer something different gets slammed as inconsistent.

That in itself holds a clue as to the coming campaign. In 2010 fears of a hung parliament and all the instability that brings were used to squeeze votes by the Tories. In 2015, they're unlikely to play on voters' worries in quite the same way.

This might, perversely, help boost the Lib Dems' chances and contribute to no party getting an overall majority. A more evenly balanced hung parliament could end up making a government as stable as this one an impossibility. Then the Lib Dems – however many survive – will really matter. And Labour will hope today's cruel laughter is long forgotten.