It's more than rumors. Alaska State Senate President Lyda Green, a Republican, has been trashing Palin every chance she can get, on the record.
Example: "She's qualified because she's old enough and a citizen. Is she prepared and ready? I really think there's a lot of doubt there. There's a picture I have in mind of someone to be VP, and it's someone with a greater variety of service--a little better background and experience. I wake up and I think about this and I think, This can't be.' It's just surreal." Source.
So much for the 11th Commandment.
From what I understand Palin didn't tow the party line with the oil companies, and that turned the party leadership against her.