Like a lot of the inside-the-beltway crowd, The New Republic's Peter Beinart suffers from the disease of saying in 1,000 words what you can say in two. Case in point: his essay explaining what made him make the wrong decision to support the Iraq war.
Repeat after me: "Because I was fucking stupid."
That goes for people I dislike, people I admire, etc. You supported the war because you were dumb. I've done dumb things too, trust me, more than you can imagine. But the one thing I do know is that I never made the dumb decision to be in favor of this horrible war.
UPDATE: August says that weakness was/is to blame. Can't say I disagree. The people who continue to support the war are among the fraidiest of fraidycats I've ever seen, more on that later.