As we have seen, Cruz is much better at knowing the nominating process and the primary delegate rules. I trust his assessment that he still has a path to victory. There are over 400 delegates either unbound or committed to a defunct candidate. After the first ballot even more will be unbound. I think it is very likely Cruz will win if it goes beyond the first ballot.
As for the GOPe inserting an outside candidate, that outdoor only appen if the rules are changed, and the rules committee will be dominated by Cruz and Trump delegates. They won’t approve such a change. Even if by some fluke such rule changes make it out of the committee, the convention delegates then have to approve the new rule. As long as Trump and Cruz delegates refuse to approve such changes, they will never happen.
Thus, the likelihood of an outside candidate even getting nominated is bill to none.
“Could only happen”
Stupid auto-correct!