As I reported a month ago, Rudy has been wooing Perry for quite some time.
I am also hearing that some social conservative leaders are now upset with Perry, and are now talking about retribution. Time will tell if this is just talk.
Why would Perry endorse Rudy? Obvious speculation is that it puts him on the short list of running mates. In fact, Perry will accompany Rudy to Iowa today, following Rudy's presentation at the Club for Growth. If this doesn't further fuel speculation that he is a possible VP pick, I'm not sure what else would.
Another interesting side story here is the fact that Perry and Romney aren't close. Some have speculated that this is due to the fact that while Romney was the head of the Republican Governor's Association (RGA), their media consultant also worked for Perry foe Carolyn Keeton Strayhorn (who was running against Perry at the time).
Personally, I think the reason may be that two dudes -- who both pay that much attention to their hair -- could never be on the same side ...