Judging by his agile performance at Tuesday’s Iraq hearings, Sen. Barack Obama (D-Ill.) now is opting for the famous George Aiken formula from Vietnam days: Declare victory and get out.

[IMGCAP(1)]Or, rather, as an update on the late Vermont Republican’s 1966 idea, Obama would declare the situation in Iraq “manageable” and drastically reduce American forces — possibly, he suggested, to just 30,000.

Of the three presidential candidates displaying their intellectual wares in questioning Gen. David Petraeus and U.S. Ambassador to Iraq Ryan Crocker, Obama surely was the most subtle and shrewd.

He also gave a bit of a hint of how he would practice his much-promised bipartisanship if he were elected president: He would coordinate and cooperate with Republicans when they agree with him.

By contrast, Sens. John McCain (R-Ariz.) and Hillary Rodham Clinton (D-N.Y.) basically delivered dueling campaign speeches over which was more “irresponsible” — too-hasty troop withdrawals or continuing present policy.

Clinton, who has rushed from Obama’s right on Iraq policy to his left in a desperate attempt to salvage her presidential campaign, joined other Democrats in refusing to acknowledge any progress achieved by President Bush’s troop surge.

Clinton said Tuesday that she favored a “responsible and carefully planned withdrawal,” but her communications director, Howard Wolfson, told reporters last month that she favored withdrawal regardless of conditions prevailing in Iraq.

She redeemed herself as a Senate leader — possibly, her future career path — by insisting that Bush submit to Congress his proposed agreement with Iraq for a continued U.S. troop presence. He won’t, of course.

McCain, whose long argument for more troops in Iraq has been vindicated by the surge’s stunning military and partial political success, did use the moment to deflect charges (especially Obama’s) that he wants to keep troops in Iraq forever.

“Our goal — my goal — is an Iraq that no longer needs American troops,” he said, “and I believe that we can achieve the goal perhaps sooner than many imagine.”

But it was Obama who took most advantage of the televised hearings to render a nuanced — even silken — performance.

In a statement rare among Democrats, he declared “we all have the greatest interest seeing a successful resolution to Iraq.” The party line is that Iraq is a “quagmire” or (Clinton’s words) a “failed policy.”

Obama acknowledged that “the surge has reduced violence and created breathing room,” although he did not take the opportunity to admit that he was wrong last year to predict that the surge would fail and to vote to cut off funds for U.S. troops.

Obama didn’t, to his credit, say that no political progress had been achieved using the surge’s “breathing room.” He just said it “has not been taken the way we all would like it.”

Iraq’s parliament has approved a pension law, de-Baathification reform and a provincial powers law that will lead to provincial elections in October. Oil revenues are being shared, and Iraq’s former Sunni-Shiite civil war has stopped.

In all, 12 of the 18 “benchmarks” set out last year for Iraqi political progress have been achieved. No one’s satisfied, but it is definite progress. This, Obama did not acknowledge.

Obama hewed to the Democratic party line in dismissing as a “parade of horribles” the likely consequences of too-hasty U.S. withdrawal — renewed ethnic violence and a collapse of U.S. influence in the world.

Allying himself with the argument that the U.S. is economically and militarily “overstretched” by Iraq, Obama cited Republican Sens. George Voinovich (Ohio), Dick Lugar (Ind.) and Chuck Hagel (Neb.).

My guess is this will be a pattern when a President Obama pushes his liberal agenda. Like Bush, he’ll try to pick off as many votes in the other party as he needs — as opposed to seeking broad bipartisan agreement.

The most interesting part of Obama’s performance, though, was his laying down of what constitutes “success” or “a manageable situation” in Iraq.

His standard seems to be “a messy, sloppy status quo but (where) there’s not, you know, huge outbreaks of violence, there’s still corruption, but the country is struggling along, but it’s not a threat to its neighbors and it’s not an al-Qaida base.”

Obama’s line of questioning seemed to suggest his thinking. He’s for setting a timetable for withdrawal to pressure the Iraqis toward political settlement and for accepting “a messy, sloppy status quo” to justify sticking to the timetable.

That’s the Aiken formula — define success down so it’s easy to justify retreat.

Crocker responded to Obama that, sure, “when Iraq gets to the point that it can carry forward its further development … with still a lot of problems, but where they and we would have a fair certitude that they can drive it forward themselves without significant danger of having the whole thing slip away from them again, then clearly, our presence diminishes markedly.

“But,” he said, “that’s not where we are now.” And that’s right. The problem with the Aiken solution — and Obama’s — is that to declare “victory” or “success” when it’s not really there is to ensure defeat.