There have been 19 televised Republican debates. They have been boring in parts, and repetitive, with the same old arguments and lines trotted out again and again. But they have been hugely significant in shaping the battle for the nomination.

Most people don't follow the day to day movements of every campaign, and so the debates become the touchstone, the place where people tune in, sit back and make their judgements. Here strengths and weaknesses are exposed and campaigns are strengthened or diminished as a result.

Texas Governor Rick Perry was a Republican front-runner, a favourite with the right of the party and a good campaigner. But his candidacy unravelled in 53 seconds during a debate where he stammered and stumbled as he tried to recall the third government department he would close down. 

Herman Cain - a man with limited political experience - suddenly found himself a front runner on the basis of some snappy and energetic debate performances. His tax mantra of 9-9-9 was criticised by opponents and economists alike as highly unworkable and detrimental to those on the lowest incomes, but it struck a chord with the viewers. His campaign was eventually put on hold under a welter of allegations of inappropriate behaviour.

And then there is Newt Gingrich. His campaign staff deserted him last summer, he had no money to mount a huge campaign, but he is a master debater. And that was enough to lift him in the polls and propel him to an unlikely victory in South Carolina. He challenges the arguments he can and ignores the questions he hates, often by attacking the questioner as part of the 'liberal media'. His combative "in your face" style has convinced many Republicans he's the guy who can challenge, debate and defeat President Barack Obama this autumn.

Interestingly, the debates also influence the media coverage in the days after. The highly respected Pew Research Center's Project for Excellence in Journalism found that the tone of coverage of a candidate almost directly corresponded with the assessment of their debate performances. So a winner remains a winner.  

And they do also shape voting intentions. In New Hampshire, which held the first primary what seems like weeks ago, 84 per cent of those surveyed in exit polls said the debates were important to their vote. In South Carolina, the figure was lower at 65 per cent. However it should be remembered going into the first primary in the south, Newt Gingrich was way behind Mitt Romney but his debate performances compared to Romney's stumbling hesitant performance was enough to hand him a significant win and propel him with huge momentum into Florida. Gingrich addressed his debating skills at his campaign's victory party in South Carolina when he told supporters: "It's not that I am a good debater, it is that I articulate the deepest-felt values of the American people".

Romney's performance was so dire, at one point his advisers were talking about missing both the debates in Florida. His campaign recruited Brett O'Donnell who coached Michelle Bachmann, and it worked. He was more focused, more coherent, put the difficult issues to bed quickly and with some style and hit Gingrich so hard that many observers at the debate - including me - thought he was the winner on the night.  And that is something no one has said since the early debates.

Ron Paul continues to pick up supporters through consistent performances and unflinching views, which remain despite attacks from the other candidates on some issues. And Rick Santorum impresses enough to gather votes, which will undoubtedly impact on any close races

The format of one-minute answers and 30-second rebuttals aren't enough to address significant and serious issues like America's debt crisis, the deterioration of the country's manufacturing base or Iran's nuclear programme. The debates are good TV they are showbiz. But they also give people an insight into those chasing their vote and they are making a difference.

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