(CNN)Republican presidential candidate Ted Cruz is using comments made Wednesday by former President Jimmy Carter in a new ad taking aim at rival Donald Trump.
Ted Cruz ad highlights Carter's Trump 'endorsement'
During a speech to the British Parliament on Wednesday, Carter -- frequently held up by the right as a liberal boogeyman -- said if he had to choose between Trump and Cruz, he would choose billionaire businessman -- not the kind of endorsement any GOP candidate wants.
"If I had a choice between Cruz and Trump, I think I would choose Trump," Carter said. "The reason is Trump has proven already that he's completely malleable. I don't think he has any fixed opinions that he would really go to the White House and fight for."
"On the other hand, Ted Cruz is not malleable. He has far right wing policies, in my opinion, that would be pursued aggressively if and when he might become president," Carter said.
The Cruz campaign quickly seized on the remarks and crafted it into a web ad.
Trump responded to the knock after an event Thursday.
"He's got good taste," Trump said of Carter.
Carter's comments have even become a part of Cruz's argument against Trump on the campaign trail.
"It was an interesting yesterday, I don't know if you guys saw. Jimmy Carter has endorsed Donald Trump. I am not make that up. This is real," he said during a rally in Portsmouth, New Hampshire, on Wednesday.
Carter's comments come as the feud between Trump and Cruz escalates. On Wednesday, Trump accused Cruz of stealing a win in the Iowa caucuses.
The controversy erupted after CNN reported Monday night that Carson would go home to Florida following the Iowa caucuses instead of flying directly to the early voting states New Hampshire and South Carolina. The network added that he planned to stay in the race.
Some Cruz allies shared that news widely on the night of the caucuses, including to Carson supporters, but did not include the part about Carson remaining in the race.
That has irked Carson and his team, who has said the decision by the Cruz team to share only part of the CNN report was a dirty political maneuver.
Trump latched onto it as a reason to invalidate Cruz's victory over him in Iowa.
Cruz won the Iowa caucuses with 28% of the vote, while Trump came in second place with 24%.