Lina Khatib is director of the Carnegie Middle East Center in Beirut. Previously, she was the co-founding head of the Program on Arab Reform and Democracy at Stanford University's Center on Democracy, Development, and the Rule of Law. The views expressed in this commentary are solely hers.

(CNN) The past two weeks have witnessed two significant advances for rebel groups -- and for ISIS -- in Syria.

ISIS recently took over most of the Yarmouk Palestinian refugee camp near Damascus. A week before that, a rebel coalition calling itself Jaysh al-Fateh -- mainly composed of ISIS rivals Ahrar al-Sham and Jabhat al-Nusra -- took over the northern city of Idlib, making it the second urban center lost by the Syrian regime after Raqqa, where ISIS is headquartered.

Lina Khatib

But the two advances are wildly different: While the fall of Idlib is a clear loss for the regime of embattled Syrian President Bashar al-Assad, the ISIS takeover of Yarmouk is a regime-blessed tactic, if not necessarily a successful one. And they are both signs that the position of the Syrian regime is not as solid as it used to be.

The regime, following the loss of Idlib, is now concerned it could also lose the southern city of Daraa, where more moderate Free Syrian Army (FSA) rebels have been making significant gains. The regime has started to move its administrative bureaus out of the area as it did just before Idlib's fall.

Yarmouk is only 100 kilometers away from Daraa. If ISIS, now in control of the camp, uses it as a base to attack the FSA in Daraa, it would save the Syrian regime from having to fight that battle itself.

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