While mainstream US polling organisations were caught out by the upsurge in support for former Pennsylvania Senator Rick Santorum in the 3 January Iowa caucus for the Republican presidential nomination, data analysts monitoring Twitter activity picked up on his rising popularity.

The website mashable.com teamed up with Globalpoint – a company that monitors social media – to produce an analysis of sentiments about the candidates expressed on Twitter. Globalpoint’s metric, which showed clearly Santorum’s rising support, was based upon a weighted combination of tweet volume and sentiment for each candidate.

The analysis forecast Santorum’s share of the popular vote at 35 per cent, in contrast with NBC’s prediction of 12 per cent. In the event Santorum polled 24.5 per cent, putting him just eight votes behind the front-runner Mitt Romney.

The US 2012 elections look likely to prove more challenging than ever for established pundits and pollsters, not least because of the new wave of data analysts tapping into social media to measure sentiment. According to Globalpoint president Michael Urban, Twitter is an important indicator of public opinion and is about two weeks ahead of polling data and elections.

Another Mashable contributor, Ethan Bauman commented “Very excited about the opportunity here; though think there’s a little nuance around how to talk about ‘predict’ when it comes to Twitter. Looking at Michelle Bachmann’s results, Twitter over stated her performance by 2x while understating Rick Perry’s performance by 2x. In that sense, the poll was a more precise predictor than Twitter. On the other hand, the polls got it wrong when it came to Santorum — we’ve found, like you did here, that analyzing (a) Twitter spikes and (b) instances where Twitter activity departs dramatically from survey data is where really valuable insights lie.”

But in a comment posted on Mashable’s story, correctnicity – a website that encourages visitors to “predict what will happen” and “earn rewards” – criticised Globalpoint’s methodology saying “using sheer volume as a metric fails to account for the nuances of the motivations behind the retweet/mention”.

Blogging at FiveThiryEight on nytimes.com, John Sides pointed out that candidates like Santorum who exceed media expectations consequently gain more media exposure. That in turn may help or hinder their subsequent performance, but will almost certainly raise their social media profile, and fuel its rapidly evolving analysis.