John McCain and Lindsey Graham both think it's time the US began to arm the Syrian rebels.

New York Times:

The senators, John McCain of Arizona and Lindsey Graham of South Carolina, both Republicans, laid out a series of diplomatic, humanitarian and military aid proposals that would put the United States squarely behind the effort to topple President Bashar al-Assad of Syria. The senators, both of whom are on the Senate Armed Services Committee, said that rebel fighters deserved to be armed and that helping them take on the Syrian government would aid Washington's effort to weaken Iran.

Syria relies on Iran for financial and military support, and the governments in Damascus and Tehran have sectarian ties as well: Iran has strongly backed the Syrian Shiite minority and the offshoot Alawite sect that makes up Syria's ruling class.

"I believe there are ways to get weapons to the opposition without direct United States involvement," Mr. McCain said. "The Iranians and the Russians are providing Bashar Assad with weapons. People that are being massacred deserve to have the ability to defend themselves."

"So I am not only not opposed," he said, "but I am in favor of weapons being obtained by the opposition."

Marc Lynch (Abu Aardvark) thinks that's a horrible idea:

First, who exactly would be armed? The perennial, deep problem of the Syrian opposition is that it remains fragmented, disorganized, and highly localized. This has not changed. The "Free Syrian Army" remains something of a fiction, a convenient mailbox for a diverse, unorganized collection of local fighting groups. Those groups have been trying to coordinate more effectively, no doubt, but they remain deeply divided. For all their protestations of solidarity, the Syrian National Council and the FSA show few signs of working well together, while repeated splits and conflicts have emerged in the media within the FSA. So to whom would these weapons be provided, exactly? I expect that what will happen is that foreign powers will rush to arm their own allies and proxies (or are already doing so); which ones are the United States meant to choose? While claims about the role of Salafi jihadists in the armed opposition are likely exaggerated, the reality is that we know very little about the identities, aspirations, or networks of the people who would be armed.

Second, how would the provision of weapons affect the Syrian opposition? Access to Western guns and equipment will be a valuable resource that will strengthen the political position of those who gain control of the distribution networks. Competition for those assets does not seem likely to encourage the unification of the fragmented opposition, and it could easily exacerbate their divisions. What's more, fighting groups will rise in political power, while those who have advocated nonviolence or who advance political strategies will be marginalized. Fighting groups' political aspirations will likely increase along with their military power. The combination of militarization and more ambitious goals will make any political solution that much less likely. And it could increase the fears of Syrian fence-sitters who have stayed with Assad out of fear for their future.

The two keys are who is going to get the guns, and how much will arming the rebels empower the Islamists? So far, the fundamentalists and the Muslim Brotherhood have been hanging back in the Syrian opposition, maintaining a fairly low profile - just as they did to one degree or another in Libya, Tunisia, and Egypt. I would want to be pretty sure before supplying weapons to the rebels that whatever political grouping forms out of the opposition, the Muslim Brotherhood has little or no chance of gaining power. As Lynch points out, the opposition is currently terribly fragmented and can't even agree on an agenda.

Better to allow the Syians to get their act together politically before we arm the rebels in what would be the final act of the Assad regime before the curtain rang down.