Wow. I didn't know a post could be over 100% wrong.
First off, neither Cruz nor Trump "support" Assad. They are disinterested in nation building. That is it. Support implies material, not just casual approval!
Second, even if they did support Assad, they're not implicitly supporting ISIS because deal making is not support either! Assad is at war with ISIS. War sometimes comes with strategic deals. Obviously if Assad had the chance, he would wipe out IS in a second. Clearly he can't. And when his country is falling apart, why not make deals to get supplies?
Third, this is not going to change anyone's mind. Benghazi is still worse than this. So is flat out training ISIS in Syria (State dept. and CIA programs).
Fourth, this is recent knowledge. Cruz didn't know this before. Why should it haunt him now?