"Amnesty is not the way to do it," Romney says in the ad.
Sen. John McCain, R-Ariz, responded this week, arguing Romney's position amounts to a flip-flop from his previous position on immigration.
"In the case of Gov. Romney, maybe I should wait a couple weeks and see if [his position] changes," said McCain on a conference call Monday to journalists. "Because it's changed in less than a year from his position before."
McCain, an author of the compromise, added with no small dose of sarcasm, "Maybe his solution will be to get out his small-varmint gun and drive those Guatemalans off his lawn," referring to a Boston Globe report that found Romney hired a landscaping service that employs illegal immigrants.
The current immigration bill is a compromise package hammered out late Monday night, which involved lengthy negotiations with the White House and congressional leaders.
Senate Majority Leader Harry Reid, D-Nev., said vehement disagreement over the bill's provisions may ultimately produce better immigration legislation.
"No one is happy. No one is taking advantage of anyone else," concluded Reid.