President Barack Obama, Mitt Romney pledge to pursue immigration reform

For example, Caldwell argued, to change the way green cards are issued, Romney would need help from Congress. Republicans have blocked legislative attempts to raise green card limits. Romney's suggestion to "field enough Border Patrol agents, complete a high-tech fence and implement an improved exit verification system" parallels the Bush administration's virtual fence plan, which ultimately failed, she said.

"Romney's plans don't take notice of what's already been done," Caldwell wrote.

At a breakfast hosted by The Christian Science Monitor, Florida Sen. Marco Rubio, the only Latino Republican in the Senate, defended Romney's immigration politics. The presidential hopeful's comments about self-deportation, or the idea of encouraging illegal immigrants to return to their native countries of their own accord, were not a statement of policy, Rubio said.

“It is an observation of what people will do in a country that is enforcing its immigration laws,” Rubio said. “And I think quite frankly some of that is happening now because of economic improvement in Mexico."

While Romney doesn't have an immigration bill "per se," Rubio said, "neither does the president."

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