A while ago I asked a related question. But my answer blew it on one major possibility. Doesn’t Andrew Sullivan have a reasonably strong claim to that title, especially after the recent Supreme Court decisions on gay marriage? Sullivan was the dominant intellectual influence on this issue, from the late 1980s on, and that is from a time where other major civil liberties figures didn’t give gay marriage much of a second thought, one way or the other, or they wished to run away from the issue. Here is his classic 1989 New Republic essay. Here is a current map of where gay marriage is legal and very likely there is more to come.
Sullivan was also a very early blogger, and an inspiration for many in that regard (myself included), and the blogging innovation seems like it is going to stick. That’s two big wins right there, and how many other people can even come up with one?
Many of you will complain about his “war blogging,” his connection to Obama, and perhaps other matters, but no matter what you think on these issues it still seems to me he holds the lead.
Pre-Sullivan, I would give the honors to Milton Friedman.