The British-born Sullivan was described recently by Tyler Cowen as the US’s “most influential public intellectual” of the past 20 years. That may be hyperbole, but Sullivan’s influence on key debates, particularly on the US federal government’s recognition of same-sex marriage, has been immense. Sullivan, a conservative, first made the case for gay marriage in the late 1980s and kept it on the agenda. Today, 36 states have legalised gay marriage. Sullivan was also a pioneer of political blogging.