I can't think of any conservative better then Cruz, I liked Paul but his is going wobbly on illegal immigration again. This is the third time and for me three strikes and you are out. Cruz IMHO is weak on foreign policy. He needs to get up to speed on exactly who our real enemies are, but he's a smart guy so I have little doubt he will get up to speed quickly.
That door has always been open. And still is.
The solution -- as it always is -- is for the electorate to do a better job of picking candidates.