Rick Santorum appeared on CNN’s “State of the Union” on Sunday as a Mitt Romney surrogate, and he was asked about his attacks on Mitt Romney: “I have no problem questioning authenticity,” he said in his own defense. Romney, he continued, would nonetheless be better than Obama.

His obviously unenthusiastic support comes on the heels of his founding of “Patriot Voices,” an outside group partially designed to pressure Romney from the right.

In his interview, he doubled down for the Tea Party candidate in the Senate primary against longtime Mitt Romney ally Orrin Hatch.

He also urged Romney to take a harder line as immigration, especially in the wake of President Obama’s decision to halt the deportation of 1 million young immigrants:

“[Romney]’s trying to walk a line as not to sound like he’s hostile to Latinos — and [voters in] very important states — but at the same time, I think you need to hammer the president on this now-habitual abuse of power,” he said on CNN’s State of the Union.