This weekend, Italians vote on the Senate elections. If the polls are accurate, Pier Luigi Bersani and his Democratic party will become the largest coalition group. But the real story might just be Beppe Grillo and his Movimento 5 Stelle (M5S).
So how well will Grillo fare? He presents a problem for polling companies. Over the past few years, polls have become more accurate: Nate Silver correctly predicted all 50 states in the 2012 US presidential election. An average of polls calculated before the polling blackout (Italy does not publish polls two weeks before an election) puts the M5S at somewhere between 15 and 16 per cent.
However, new/populist/radical parties like the M5S can confound predictions for a variety of reasons. In the 2012 French presidential elections, Jean Luc Melenchon, a populist radical left wing candidate, was predicted to score betwen 12 - 15 per cent, but ultimately secured only 11 per cent on election day, while Marine Le Pen and her radical right Front National were underestimated, gaining 20 per cent. Most radical right parties tend to benefit from a 'curtain bonus' - people are embarrassed to admit their preference to a polling company, only to cross the box in the safety of the booth. By contrast both Hollande and Sarkozy ended up close to the pollsters' predictions.
But Grillo is awkward. A relative newcomer to formal politics, he is a comedian who launches funny tirades at other candidates (he calls Berlusconi 'psycho-dwarf'), he refuses to speak to the Italian media, and despite being the leader of the M5S party, won't actually be standing for election himself. Ordinarily this would probably mean Grillo's support is overestimated by the polls. Yet normal rules don't apply. Grillo has, by an enormous margin, the largest social media following in Italy - in fact, in Europe.
He has over one million Facebook friends, and a similar number of Twitter followers (Bersani has about a quarter of that). He uses this huge social media profile to make things happen offline. Grillo has constantly encouraged his supporters to discuss the issues he raises on his blog as they relate to local questions in their cities and towns. For example, as of 8th November 2012, there were officially 532 Grillo meet-up groups, containing 87,895 members spanning over 400 cities. This sort of local organisation used to take years to build. Our recent report about his supporters showed they are motivated and mobilised - which means ready to get out and vote, and encourage their friends to as well. This can make a huge difference if apathy is high for other parties. In 2011 the Internet-based Pirate Party were expected to receive five per cent of the vote for the Berlin House of Representatives: they managed nine.
For a pollster this election will be something of a litmus test. Will social media campaigning and support translate into actual votes? I think it will. He won't have the curtain bonus of stigmatised far-right parties and candidates, and inside the booth some voters might think again about voting for an unknown is too risky. But his enormous social media following should weigh in his favour. Taken together then, I'm placing the probable result at somewhere around 18 - 19 per cent. Not confounding the pollsters by much, but certainly enough to make any politician with a looming election take serious note.
Follow Jamie Bartlett on Twitter: www.twitter.com/JamieJBartlett