Chris Cillizza reports that Giuliani is planning on announcing the creation of an "Immigration Advisory Board" today and further outlining his position on immigration--perhaps as a result of Romney's attacks on Giuliani's record on immigration.
UPDATE: Guiliani announces his board of advisers:

Serving as the Mayor’s Chief Homeland Security Advisor is Robert Bonner, former Commissioner of the U.S. Customs and Border Protection Agency and former Administrator of the Drug Enforcement Agency. Stewart Verdery, Jr., the former Assistant Secretary for Policy and Planning at the Department of Homeland Security, will serve as Senior Immigration Advisor. Other members of the advisory board include Victor Cerda, Michael Petrucelli, Nicolle Sciara Rippeon, Ray Shepherd, and Jan Ting.