If Trump were elected, he would certainly not follow this. Assad is Iran's best ally, by the way, as Assad's Alawites are a Shia group.
The dumbest of the bunch is Cruz, who thinks carpet bombing cities in which 90% of those killed would be mostly noncombatant civilians.
The US did not cause the Syrian Civil War, and it will not be decided by force of arms, no matter who wields them.