But it was the way he crafted this argument that (to me, anyway) initially awoke my doubts about his conservative credentials. Consider the opening two lines: "I suppose I first developed a fondness for the flat tax when both Jerry Brown and Steve Forbes supported it. It had that energising Right-Left whiplash I've rarely been able to resist." There is a huge Right-Left dichotomy on tax reform — and support for the flat tax is overwhelmingly on the Right. 

Conservatives have always promoted ideas that make sense to us, and in turn, make sense for our respective countries; acquiring the support of left-wingers is rarely on the political radar.  So why was it important to Sullivan that the Left was onside?

When you start to examine his other political positions, it begins to make more sense.  

Sullivan is left-leaning on most social issues, including his opposition to capital punishment, criticism of the war on drugs, and support of same-sex marriage. In fact, Sullivan (who is gay) has written so extensively on sexual politics that it seems to have had a lasting effect on his opinion and analysis. Many conservatives have noticed this. In one noteworthy example, Tunku Varadarajan, Elisabeth Eaves and Hana R. Alberts correctly observed in their 2009 Forbes piece, "In Depth: The 25 Most Influential Liberals In The US Media", that Sullivan's "advocacy for gay marriage rights and his tendency to view virtually everything through a gay prism puts him at odds with many on the Right."

In terms of foreign policy, Sullivan is sharply to the Left. He initially supported the war on terror and the 2003 Iraqi invasion, but eventually withdrew that support in favour of a mushy, isolationist position. He has become increasingly critical of American initiatives abroad, and his distaste for neoconservatism has intensified.

  Israel has also become a favourite target.In a Sunday Times column last month, Sullivan decried the fact that "the all-mighty Israel lobby convened in Washington and swamped Capitol Hill with visitors raising the spectre of Auschwitz". He went on to describe the worldview of Israel's prime minister Benjamin Netanyahu (not Iran's Mahmoud Ahmadinejad) as "Manichean" and "apocalyptic". Rather extreme language, especially from someone who has  in the past claimed to be a Zionist.