“The danger is that you have a wide chessboard and lots of moving pieces,” said a senior Arab diplomat who requested anonymity in order to speak freely. “The situation is very serious and fast-moving.”

The crisis could easily reach a point “where the downside risks of doing nothing begin to outweigh the risks of doing something,” Larrabee said.

A re-elected President Obama could develop a new strategy faster than a newly elected Romney, who’d need months to seat his full national security team and conduct a policy review, the senior Arab diplomat noted.

Neither Obama nor Romney has spent much time during the campaign discussing the bloodiest of the Arab uprisings that have upended the Middle East. But both largely espouse the same approach: oust Assad and stop Syria from becoming an Islamist haven by using the CIA to steer Saudi- and Qatari-supplied arms to moderate rebels while trying to unify disparate opposition leaders with the credibility to be a government-in-waiting that would participate in a U.N.-led peace effort.

Obama has sent a U.S. military taskforce to Jordan’s border with Syria to help Jordan forge contingency plans in case of a spillover of serious violence, and he has slapped sanctions on the regime to strangle its arms buying. The United States also has provided more than $132 million for assistance to hundreds of thousands of refugees – estimates place the number between 360,000 and perhaps 700,000 – outside Syria and the millions of people – somewhere between 1 million and 10 million – who’ve been forced from their homes by the fighting and are now scrambling to find food, shelter and medical care.

The U.S., however, has rejected calls to impose a no-fly zone to ground Assad’s airpower and refuses to supply heavy weapons, including shoulder-fired anti-aircraft missiles, to the rebels, fearing the weapons would end up in the hands of al Qaida-linked Islamists.

The bloodletting – estimates of the dead are nearing 40,000 and may be much higher – also is having a corrosive effect on U.S. relations in the region, experts said. Both Turkey and its Arab allies, frustrated by what they consider a standoffish U.S. role, are outrunning current policy.

“The U.S. has lost a lot of leverage and it’s coming into this particular game too late,” said Ammar Abdulhamid, a Syrian dissident and fellow at the Foundation for the Defense of Democracies, a center-right policy institute in Washington.

Still, he and other experts said, the U.S. can’t stop exploring its options, especially with the war heating up sectarian tensions in Lebanon, where there have been gunfights between Alawites and Sunnis and an Oct. 19 car-bomb assassination in Beirut of a senior Sunni police official that many blamed on Syria and Hezbollah.

The war also is infecting Iraq, threatening to upend the tenuous stability that the U.S. fought for nine years to secure. Iraqi Sunni militants are siding with Syrian rebels, Shiite extremists are fighting for Assad, and the Shiite-run Baghdad government is reportedly allowing Iran to send arms to Damascus across its territory and airspace, stoking frictions with Saudi Arabia and other Sunni Arab regimes.

Turkey, meanwhile, has made clear that it won’t tolerate Syria’s minority Kurds setting up an independent enclave in northeast Syria that is run by the Syrian wing of Turkey’s Kurdish rebels and that could enflame Kurdish separatism in Iraq and Iran. In recent days, Syrian Kurdish militia have clashed openly with anti-Assad rebels near Aleppo.