WASHINGTON — THE winner of the Nobel Peace Prize had been up late pleading for war.

The president looked exhausted as he met the press in St. Petersburg on Friday. The man elected because of his magical powers of persuasion had failed to persuade other world leaders at dinner the night before about a strike on Syria.

He said he had told his fellow leaders, “I was elected to end wars and not start them.”But in life, and especially in Washington, people sometimes end up becoming what they start out scorning.

It is uncomfortable to watch the president struggle to reconcile his two conflicting identities as he weighs what he calls the unappetizing choices on Syria, and as he is weighed down by the malignant choices on the Middle East made by his predecessor.

In his head, is Barry at war with the commander in chief?One side of him is Barry, the smooth consensus builder and community organizer, the former constitutional professor and the drive-by senator who must stand by the argument he made when he ran for president excoriating W.’s and Dick Cheney’s highhandedness: checks and balances must be observed. As he told Charlie Savage, then reporting for The Boston Globe, in 2007, “The president does not have power under the Constitution to unilaterally authorize a military attack in a situation that does not involve stopping an actual or imminent threat to the nation.”W. and Tony Blair were not honest about the imminent threat from Saddam. President Obama said in Russia Friday that “I put it before Congress because I could not honestly claim that the threat posed by Assad’s use of chemical weapons on innocent civilians and women and children posed an imminent, direct threat to the United States.”When it came time to act as commander in chief, he choked and reverted to Senator Barry — even though many lawmakers in both parties privately wish the president had just gone ahead and hurled a few missiles, Zeus like, and not put them on the spot.

Now the president who saw no benefit in wooing Democrats on the Hill is desperate for their love. Nancy Pelosi, the San Francisco peacenik, will have to win Barry the right to bomb.

Those around him say that, after the British poodle slipped its leash, Obama faced a gut check on his decision to have a strike. He had to dig deep and decide “This is who I am,” and be true to himself. To be Barry, president of the Harvard Law Review.

In some ways, his reaction reflects his tendency toward mixing high principles with low motives. He believes it is proper to get Congressional approval and let the people chime in. But he also wanted to make life difficult for Congressional Republicans who like to “snipe,” using his word, from the sidelines with no accountability. He wanted to call their blustery bluff.

But who is going to get bluffed?Obama had to know that once he threw this into the Congress, it was likely done for. Congress now is a paralyzed domestic version of the U.N., with Republicans going “nyet” as often as the Russians, and Democrats acting like the don’t-look-at-us-for-help Chinese.

Many Republicans are trying to use this as an attempt to emasculate the president, but can they really send the message that the U.S. president is weak?Obama has told Israel, when it has threatened to go it alone on striking Iran, to back off, guaranteeing the U.S. would use force if necessary to prevent Iran from getting a nuclear weapon. If Congress ratifies that there’s no appetite among Americans to police the Middle East, does it doom any chance of a U.S. pre-emptive strike on Iran and indicate that the U.S. won’t be there for Israel?Barack Obama first made his mark as an Illinois legislator with a speech in 2002 about Iraq, which he warned would be “a rash war, a war based not on reason but on passion,” a war that would “distract” from our own problems with the economy and poverty.

Now agitated constituents at town halls across the country are asking why the president wants to distract from our own problems with the economy and poverty.

As Maryland Congressman Elijah Cummings said on NPR, a nurse at Johns Hopkins confronted him, saying: “Folks have been using chemical weapons for a long time. Do you realize when I took my son to school, they didn’t even have books for him to” learn from?As commander in chief, Obama knows that if he doesn’t punish Bashar al-Assad, America and his presidency will be forever reduced. He thinks a limited strike — not a war, as some are calling it — is the right thing to do.

But as Barry talked to the press in St. Petersburg, his lack of enthusiasm came across. He was not thundering from the top of the moral ramparts. He made his usual nuanced, lawyerly presentation, talking about the breach of international “norms.” It’s a weak, wonk word.

Norms don’t send people to the barricades.