Former Massachusetts Gov. Mitt Romney will endorse Marco Rubio over Gov. Charlie Crist in Florida's Republican Senate primary. Romney plans to announce the endorsement Saturday, according to a Romney adviser who asked to remain anonymous because the official announcement has not been made. Romney is the third major 2008 presidential candidate to endorse Rubio. Former New York Mayor Rudy Giuliani and former Arkansas Gov. Mike Huckabee have also endorsed the former House speaker. The adviser said Crist and Rubio both sought the endorsement, but Romney believes Rubio has a stronger conservative record and is an idea-driven leader. Romney's PAC is...