“Ignore the ‘Twindex’ at your peril,” warned Chris Cillizza yesterday on The Fix, a Washington Post blog.

The which?

Twindex (n.) is a catchy abbreviation for the Twitter Political Index, a joint endeavour by the identity-shifting microblogger, data analysis company Topsy and pollsters Mellman Group (Democrat-leaning) and NorthStar Opinion Research (Republican-tilting) to take the political pulse of the United States of America by indexing the 400 million 140-character statements pronounced each day – by sentiment.

That is, Topsy sifts through this onslaught of daily tweets from around the world to establish a neutral baseline of positive and negative sentiment. It then sifts through them to find all of the tweets that express opinions about President Barack Obama and soon-to-be-anointed Republican rival Mitt Romney, runs a “sentiment analysis” on them, and weighs them based on how enthusiastic or disparaging they are compared to the baseline. It looks at the last three days of tweets, weighting the more recent ones higher.