Ted Cruz finally located Marco Rubio’s weak spot: immigration.

After a somewhat rocky first hour on the debate stage, Cruz had an opening. Moderator Dana Bash directed a tough question about immigration toward Rubio, who sponsored a bipartisan bill in 2013 that would have extended a pathway to citizenship to undocumented immigrants.

“There was a battle over amnesty,” Cruz chimed in, pointing out that some politicians, like Rubio, chose to back President Obama and Democratic Senator Chuck Schumer.

Rubio, visibly shaken, responded: “I am always puzzled by his attacks on this issue,” pointing out that Cruz has supported “doubling the number of green cards.” 

“I led the fight against his legalization and amnesty bill,” Cruz said. “He was fighting to grant amnesty and not to secure the border.” He added that suggesting that their plans are the same is like confusing an arsonist and a firefighter because they were both at a fire.

“We will build a wall that works, and I’ll get Donald Trump to pay for it,” he said.