Rubio drew howls — and not just from libertarian isolationists — when this spring he pushed out a thick slice of campaign hyperbole: “Nothing matters if we aren’t safe.” And this week, his eager-beaver approach to toughness drew fire from The Onion — never a good sign. “Vowing to hunt down and destroy every last vestige of the extremist group, Senator Marco Rubio announced Tuesday that his presidential campaign was deploying 6,000 ground troops to the Middle East to combat ISIS militants,” joked The Onion.

Of course, ISIS has trampled its way into the immigration debate, too. Rubio tardily flipped his stance toward keeping out Syrian refugees, while Cruz took a beating from McCain — and liberals — for suggesting that Christian refugees, and not Muslims, should be greenlit for U.S. resettlement.

The political terrain is still shifting, but one thing is clear. As a litmus test for Rubio and Cruz, immigration ain’t what it used to be. Rubio successfully broke away from the pack by pivoting out of his right-wing apostasy on immigration. Cruz, though tough enough on immigration to have blasted Rubio, had lapses of his own in the past. At September’s Values Voter Summit, Rick Santorum inveighed against Cruz’s onetime amendment “to allow people to stay in this country indefinitely. To me, that is amnesty,” Santorum cried.