From an American perspective, there was a clear winner of Britain's first-ever prime ministerial TV debate: Nick Clegg. He looked sharp, was consistently articulate, and was able to challenge the other two candidates pointedly and effectively. By contrast, the other candidates gave unmemorable performances. Just as advertised, the incumbent prime minister seemed to belong to a pre-television era. Gordon Brown came across as old and leaden without seeming especially wise. David Cameron was stiff and occasionally uncertain, with an upper-class manner that appeared high-handed at times.

Having said that, Clegg had it easy. Almost no one thinks he's the next prime minister, so the pressure was off. Both Brown and Cameron were respectful and friendly because they covet his voters. Both the Labour and Tory candidates occasionally used Clegg as a battering ram against the real opponent.

In an American context, the three party leaders were marvellously articulate, putting US politicians to shame, including Barack Obama – who can be stilted without his teleprompter. This was a debate steeped in details and policy. There were plenty of memorised soundbites, yet the format encouraged quick thinking and gave voters a sense of the mental agility of each candidate.

The subjects of the questions were familiar to anyone who watched the 2008 US presidential clashes: immigration, education, the healthcare system, and war casualties. The answers were different, for sure. Americans wouldn't necessarily have recognised the reasonable, constructive, multi-party approach to immigration, the informative commentary about educational reform, and the consensus about the worth of government-organised healthcare. Only the sobering exchange about Afghanistan caused deja vu.

The debate wasn't perfect. The exchanges were too short, too often interrupted, and difficult for viewers to interpret. The most vital question for the viewer: who was right and wrong on the facts of each subject?

The post-debate fact-checkers have a big job to do, and voters need to pay attention. If a candidate frequently misstated or invented arguments, he should be punished for it. Exaggeration is a part of politics, but there is a difference between stretching the truth and breaking it. As many US presidential debates have proven, a serious gaffe can cost a party millions of votes.