A new poll by Rasmussen claims that Rick Perry is the front runner based on the act that he is eleven points ahead of Mitt Romney. However, one poll doesn't make him the front runner.
Rick Perry doesn't have the organizational and financial resources yet justify him as a frontrunner becuase he's still working to get that in place. Mitt Romney already has campaign organizations in all 50 states and has the financial resources to keep these teams running. Also, Mitt Romney is doing well in fundraising whereas Rick Perry may be heading for trouble with fundrasing even though he just barely jumped in the race.
Besides, as Karl Rove explains below, Rick Perry isn't competing against Mitt Romney but he's competing against other 2012 candidates who will want to become the alternative to Romney in the GOP primaries: