Syria's neighbors are watching with ambivalence as President Bashar al-Assad's government confronts opposition rallies that pose the most serious challenge to his autocratic rule.

Turkey, Iraq, Jordan, Lebanon and Israel have all had tense relations with Syria at one time or another. Yet none of them are eager to see the Assad dynasty's four-decade-old rule end because they fear that its downfall would leave a power vacuum in Syria that could further destabilize a region already in turmoil.

Another...