1. To accomplish what he says he is trying to accomplish i.e. the reining in of Obama, the stopping of the Iran deal etc.
2. To expose Rino Republicans and get them on record which they have been quite artful in avoiding up till now even when they no longer have Harry Reid to thank.
3. To get himself elected president.
I'm not sure whether Cruz has one or all of these motives nor can I venture which he finds the most attractive.
Personally, my number one is illegal aliens. If we do not stop this effusive influx of unknown, unchecked refuse from the third world, all other options pale in comparison to me. The implications of stress on our justice system, support system, school and medical system - virtually all walks of life are dire to the most extreme extent.
A wide open southern border is also begging not only for the refuse, but for any insane terrorists the Muslim world wants to throw at us.
Iran? This administration has had 6.5 years of allowing anything and everything, giving up everything, ceding everything as a concession to resistance it encounters. They then get on TV and say “we got this. Trust me.”
My gut feel is that the only way to fight this America-hating Muslim is to take away all his money. Every damned bit of it.
It doesn't stop the Iran deal: the way to do that was to defeat Corker, which HE SIGNED ON TO.
This does just the opposite of "exposing" RINOs because it allows them to hide behind, "No, I voted for a highway bill. I never got a chance to vote on Iran/Obamacare." It's just the opposite: he provided perfect cover for them to avoid a public vote.
He hurt himself on #3.