CNN: Ben Carson slams Trump's 'double whammy' immigration plan

Washington (CNN) Republican presidential candidate Ben Carson joked Tuesday about the prospect of joining a Donald Trump ticket, but he split with his would-be running mate on his signature issue: immigration, saying that deporting 12 million undocumented immigrants is impractical.

Carson made his first major break with Trump since the primary race began during an appearance at the Commonwealth Club of California in San Francisco.

"It sounds really cool, you know, 'Let's just round them all up and send them back,'" Carson said. "People who say that have no idea what that would entail in terms of our legal system, the costs - forget about it. Plus, where you gonna send them? It's just a double whammy."

The two outsider presidential hopefuls have until this point had a friendly relationship with each other, absent the feuds and insults that have defined Trump's relationship with most other primary opponents.

But Carson's criticism of Trump's immigration proposal could free up Trump to begin lobbing attacks Carson's way while still remaining a counterpuncher.

More: www.cnn.com