Explaining the Senate’s Surge in Support for Same-Sex Marriage

While the public’s increase in support for same-sex marriage has been exceptionally linear and steady, the number of senators endorsing it has increased at exponential rates. Can this be explained in a mathematical model?

via FiveThirtyEight http://fivethirtyeight.blogs.nytimes.com/2013/04/04/explaining-the-senates-surge-in-support-for-same-sex-marriage/