Marco Rubio thinks he has Ted Cruz right where he wants him: On the wrong side of national security politics after a harrowing terrorist attack.

The Florida senator and his aides are pounding Cruz for his support of surveillance reforms that became law this spring over the objections of Rubio and old-school defense hawks.

It’s a calculated risk to say that Cruz weakened national security: Many Republicans sided with him in a vote that split the party over how to balance surveillance reforms with national security. But the Rubio campaign believes this is its opening to expose Cruz as being in step with Democrats on an issue that will drive the next three months of the campaign.

Late Tuesday afternoon, Cruz fired back and said that Rubio is trying to distract from his record of working on the Senate’s comprehensive immigration bill, the subject of a protracted dispute between the two campaigns over the past week.