Even as evidence mounted that Assad's military launched the Aug. 21 chemical attack, Russia insisted that the rebels were to blame. Until now, the Russians have used or threatened to use their Security Council veto to block U.N. action to punish Assad.
Despite a civil war death toll above 100,000 in Syria and millions more made refugees, Putin is banking on the world seeing the contrast between his steadfastness in standing with an isolated Syria and Obama's less than sure-footed handling of the crisis.
Besides calling for Assad's overthrow on two occasions, Obama had said Assad's use of chemical weapons would cross a red line. Obama pledged to arm Syrian rebels but the flow of arms has been minimal and sluggish.
He prepared Americans for airstrikes after the chemical attack, had Secretary of State John Kerry deliver an impassioned argument for striking Assad, then pulled back and asked Congress for support. He hasn't gotten it.
The rebels feel cut adrift, abandoned. In less than a week they went from optimistic expectations of a greater weapons flow and a U.S. air assault to degrade Assad's forces to the reality of Russia, Syria's No. 1 ally, involved in a lengthy chemical weapons process with Washington, the rebels' would-be mentor.
On the opposition front, Obama and Putin appear to share common concern.
While the Syrian uprising began as an internal matter, the rebels were in dire need of military assistance and were far outnumbered. The manpower vacuum has been filled by foreign Islamic extremists.
Neither the United States nor Russia wants to see a strategic country such as Syria come under control of religious extremists. Russia is particularly concerned given its long southern border populated by Muslim countries that were once Soviet republics.
Moscow spent nearly two decades crushing an Islamic uprising in Chechnya, a Russian republic in the Caucasus region in the deep south and not far from Syria. The U.S. worries about the further spread of territory under control of militant Islamists and al-Qaida franchises.
Both Obama and Putin will find satisfaction, for different reasons, in having avoided - again for the time being - a U.S. attack on Syria.
For Putin, the talks bolster Moscow's global standing and could, either through delay or success, preserve their crucial Middle East ally.
For Obama, a deal would pull him out of a deep political hole, the one he created for himself by declaring a readiness to strike, then pulling back in an attempt to share the responsibility with Congress, which wanted no part of an attack.
But now, should the deal fail to take chemical weapons away from Assad, Obama would again find himself having to decide whether to stand down or act, likely without support of Congress, the American people and a U.N. resolution. All options could weaken him for the rest of his second term.
Even so, supporters claim Obama has gained strength, contending his threat to use force precipitated the Geneva talks between Kerry and Russian Foreign Minister Sergey Lavrov, who jointly announced the deal.
Either way, he seems to have had little choice.
"I think President Obama is absolutely right to walk down this diplomatic path with Putin and to agree initially that we'll accept the proposal for a diplomatic solution," Burns said. "He had to do that. If there's a chance to resolve this peacefully, then we have to take it. But I think this proposal may have lots of internal difficulties and contradictions."
Burns said the United States "is in such a disadvantageous position that we need to be very tough right now."
But Putin, too, has a history of extreme ruggedness in global give-and-take, almost always taking more than he will give.
