Former Pennsylvania Senator and presidential candidate Rick Santorum is backing Donald Trump.

Why? The Supreme Court.

In an interview with Greta Van Susteren of Fox News, Santorum explained how he was impressed with Trump’s list of possible Supreme Court appointees and revealed that he spoke to The Donald over the phone about them.

“My number one thing was, give me a list of candidates that you will pick from and pledge to pick from that list,” Santorum says he told Trump during their conversation. “If those names are names that I can support, I will endorse you for President.”

Santorum described his backing of Trump as “100 percent”.

His interview with Van Susteren begins in the video above at about the 1:05 mark.