The conventional wisdom dictates that debates between VP candidates are nights that should only interest political anoraks. But the last eight days have not been good for conventional wisdom: remember how boring Mitt Romney was meant to have no chance against a man of Barack Obama’s élan?

Far more than any recent presidential debate, last night’s vice-presidential one was genuinely absorbing, pitting two contrasting, combative and forthright politicians against each other. They were helped by the performance of the moderator, Martha Raddatz. She was far more willing to engage the candidates than Jim Lehrer last week, providing the best possible opportunity for a stimulating debate. And that is certainly what we got.

Joe Biden’s debate performance was almost the antithesis of Obama’s. Where Obama was diffident, Biden was forceful; where Obama lacked figures, Biden was armed with statistics. And, most importantly of all, where Obama looked worn down by four years of political fights, Biden proved he had not lost his fight. After last week’s debate, a horror movie for many Democrats, Biden also benefited from comparatively lower expectations. He didn’t actually need them: most people who saw the 2008 Democratic primary debates would agree that Biden is a much better debater than Obama.

Predictably, Biden tried to make up for Obama’s mistake in not highlighting Romney’s tax rate and 47 per cent comments. But his attacks on the Romney-Ryan ticket were substantive. Biden was particularly effective in highlighting that they have not specified any of the loopholes that they will close to pay for gargantuan tax cuts, and shrewdly contrasted this with the specific budget-cutting measures outlined by Ronald Reagan before his election victory in 1980. His accusation of the Republicans as ‘holding hostage the middle class tax cut to the super wealthy’ reaffirmed the terrain on which the Democrats feel they can beat Romney, while Biden’s denunciation of Paul Ryan for requesting stimulus funds for Wisconsin while opposing the recovery fund was also effective.

Yet Biden’s punch did not come without a price; with him it rarely does. He has always been liable to be caricatured, mainly for his penchant for gaffes. While avoiding those, his debating style descended into self-caricature as the night progressed, relentlessly interrupting Ryan, and grinning in mockery at his answers. It certainly didn’t sound particularly presidential – but after Obama’s lethargy last week that wasn’t the point.

Just as Mitt Romney did last week, Biden essentially set the terms of the debate. He largely did so through focusing on the Republicans’ positions, as Ryan asserted. It is a sign both of how difficult a re-election campaign this is for the Democrats – though it would be harder still had unemployment not just slipped below 8% for the first time in Obama’s presidency – and the nature of the Republicans’ plank, which is significantly to the right of John McCain’s in 2008.

But, considering the attacks he faced, and that Raddatz’s emphasis upon foreign policy issues did not suit his expertise, Ryan coped fairly well. He has risen very far, very quickly – remember few Americans outside Wisconsin knew his name before the start of Obama’s presidency. Notwithstanding some difficulties, Ryan’s poise did not suggest tonight marked the culmination of his rise. One effect of a Romney victory in 26 days would be in delaying a Ryan presidential bid from 2016 to 2020.

Conversely, if Biden is to make a viable presidential bid, he needs to do so as sitting Vice-President in 2016. His performance marginally increased the chances he will be able to do so; Biden made a far more compelling case than Obama last week for a second term. Suspicions that he may have over-reached in the sheer number of his attacks on Ryan may have some basis, but they miss a larger point. Counter-intuitively, swing voters aren’t really what matter anymore, because they aren’t many of them around.

If Obama loses next month, it will be because his base stayed at home. A recent NBC / Wall Street Journal poll of registered voters, showed Republicans were 6 per cent more likely to be ‘highly interested’ voters than Democrat, a 19 per cent swing in their favour from 2008. Biden’s performance will have done something about that gap. On that basis, and without equating it in significance to the two debates that still remain, this was a reasonably successful night for the Democrats. It was also – continuing the recent burst of challenging conventional wisdom – a reminder that debates are allowed to be entertaining.

Tags: Barack Obama, Democrats, Joe Biden, Mitt Romney, Paul Ryan, Republicans, TV debate, US politics