* In Chile, Obama puts forth his doctrine, defending the Libya mission by claiming that humanitarian interventionism is the “core principle that has to be upheld.”

Crucially, Obama also took a tacit shot at Bush, comparing his own multilateral approach favorably to the former president’s:

“In the past there have been times when the United States acted unilaterally or did not have full international support, and as a consequence typically it was the United States military that ended up bearing the entire burden.”

* VoteVets, the progressive veterans’ group that got lots of attention for its full-throated opposition to the Iraq War, becomes the first major antiwar group to criticize Obama’s Libya mission, withholding support until key questions are answered.

* Must-read from Matt Duss and Michael Cohen on how the Libya mission suggests that our foreign policy elites have already forgotten the real lessons of the misguided rush to war in Iraq.

* Andrew Sullivan cuts to the core of why neocons are demanding regime change in Libya: It would somehow allow them to claim “vindication,” which is apparently more important than anything else.

* As Joe Klein notes, those neocons who are deriding Obama as adverse to using force have somehow conveniently forgotten his escalation in Afghanistan.

* Justin Elliott explains why Obama’s claim that the Libya mission is essential to our national secuirty is perfunctory and glaringly self-contradictory.

* Senator Richard Lugar, whose comments on the war are being watched carefully by the White House, ramps up the criticism: “there is no mission and there are no guidelines for success.”

* A new CNN poll finds that only 50 percent approve of Obama’s handling of Libya, which seems a bit low when compared to public support at the outset of other military ventures, but 70 percent support the establishment of the “no fly zone.”

* The relatively low support is driven by the fact that no matter what Obama does, he’ll never win the approval of the GOP base on anything.

* Claire McCaskill admits that she failed to pay $287,000 in back taxes on that McCaskill-owned private plane that keeps dropping political bombs on her, potentially big trouble in a crucial Senate race.

* Prediction of the day, from Brian Beutler: “there’s now a small but real chance that the 2012 campaign will feature Obama taking shots at Republicans from the right on Libya, and Republicans taking shots at Obama from the left on Social Security.”

* Bonus prediction of the day: A top architect of Obama’s health reform law predicts he will “campaign heavily” on it in 2012.

* And Jonathan Bernstein on why talk that Republicans may be open to tax hikes as part of a deficit deal should be regarded with extreme skepticism.

What else is happening?