Newt is calling for illegal immigrants -- should they be good citizens and have roots in the community -- to be legalized. But not become citizens.
Mitt Romney, on the other hand, is for making illegal immigrants citizens.
Of course, he is trying to cover that up now -- as he is with his previous pro-abortion and anti-gun views (along with a host of other liberal views).
For more on Newt's immigration proposal: http://www.newt.org/answers#DREAM