Cruz's new weapon against Trump: Jimmy Carter

Sen. Ted Cruz on Thursday found a new way to attack rival Donald Trump, in the form of former President Jimmy Carter, a liberal president who not only said he'd prefer Trump over Cruz, but said he doesn't believe Trump holds any real conservative positions.

Carter essentially wrote a primary campaign ad for Cruz, when he told an audience in London Wednesday that Cruz has firm, conservative convictions, while Trump would likely prove to be a much more flexible president who could work with Democrats.

"Trump has proven already he's completely malleable," Carter said. "I don't think he has any fixed [positions] he'd go the White House and fight for."

"On the other hand, Ted Cruz is not malleable," he added. "He has far-right wing policies he'd pursue if he became president."