A new Rasmussen:

The immigration reform debate may be shaking up the race for the Republican Presidential nomination. Former Massachusetts Governor Mitt Romney has inched past Arizona Senator John McCain for second place in the latest Rasmussen Reports national telephone poll. Just two weeks ago, Romney was in fourth place among GOP hopefuls.
Former New York City Mayor Rudy Giuliani (R) remains on top with 25% support. This week, Giuliani is followed by Romney at 16%, McCain at 15%, and former Tennessee Senator Fred Thompson at 12%. While Romney’s one-point edge over McCain is statistically insignificant, it’s worth noting that McCain had a six-point advantage over Romney just two weeks ago.