This Ted Cruz ad is a model for how Republicans can attack Marco Rubio’s most glaring weakness.

A super PAC allied with the Cruz campaign released its latest ad online late Tuesday night. Entitled “Marco’s Path,” it hammers Rubio for sponsoring and then backing away from the comprehensive immigration reform bill that he worked on with the Gang of Eight in 2013. 

The ad includes a particularly damning clip of Chuck Schumer, the Democratic senator from New York widely reviled on the right. “His fingerprints are all over that bill,” Schumer says. “He molded it, he made it.” 

Rubio has been the target of numerous attack ads this week, with Right to Rise, the super PAC propping Jeb Bush up on the airwaves, releasing an ad on Monday called “Vane.” The 30-second spot likened Rubio to a weathervane, shifting his positions on comprehensive immigration reform wherever the wind blows.

None, however, are as brutally effective as this latest attack, which successfully reminds voters that Rubio—far from the die-hard conservative he says he is on the campaign trail—worked with Democrats on one of the Obama administration’s top priorities.