I was vehemently against our incursion into Iraq in 2003, but now that we screwed things up then, we have a responsibility to fix it now (we broke it; we own in).
Though I believed in 2003 we were being sold a bill of goods (starting with the whole concept of "weapons of mass destruction", something designed to sound ominous just to scare people) until I heard this great NPR piece in February 2003 about the Cons belief that Iraq was ripe for democracy and once Iraq "fell" to democracy, we would have a tsunami of democracy in the middle east. The Bush legacy would be to solve the middle east once and for all. Then it all made sense, as being threatened by some two bit dictator sure did not. Of course, this tsunami of democracy would not sell; but "weapons of mass destruction" surely would scare the pants off an America just off 9/11. So, it was a bill of goods.
Then came is whole "coalition of the willing", which upon further review, given money and promises made, was really the coalition of the billing... and a roster of world powerhouses like Honduras behind it. Unlike Bush I, that actually had a coalition, this looked failed from the get-go. I figured if Iraq's arab neighbors did not see Saddam as a threat, he wasn't a threat... and, anything we did would just come off as US imperialism (over OIL --- in fact, wasn't an operation name Operation Iraqi Liberation, until they figured out the acromyn would not sell?)
That said, just as in 2003, if we do not have Arab nations (and now, specifically Sunni nations) committing a significant ground effort, everything will be for naught. Therefore, I am for military action only if we have legitimate Sunni partners, otherwise, we probably should do nothing as there is no point in doubling down on stupid.