Sen. Ted Cruz appears to be shifting his attacks to his senate colleague Marco Rubio and away from frontrunner Donald Trump, according to a report in the New York Times.

According to the report from Jonathan Martin, two advisors to Cruz confirm that the campaign is directing more attack ads against Rubio after watching him tick upwards in recent polls in Iowa.

The attack ads will focus on Rubio’s support for immigration reform, a topic that was central to the Fox News debate on Thursday night.

Cruz reminded voters that Rubio worked with liberal Sen. Chuck Schumer on amnesty for illegal immigrants and Rubio accused Cruz of just trying to “trump Trump” on the issue to get elected.