If Palin runs she'll win the GOP nomination in a walk. It will be over when the SC Primary is over. She would win Iowa, show very well in NH and win SC and NV by 30%. Nationwide polling (the real stuff, not what we get to see) will show her ahead nationally by 20 pts and rising.
If Romney is in the race, there is no way Palin comes close in New Hampshire or Nevada. Romney was over 50% in Nevada and over 30% in New Hampshire in 2008 in a losing effort...those are establishment Republican states and will not vote conservative.