How many Governors, Democrat or Republican, resigned their office suddenly halfway through their first term? And with a vague explanation and the unspoken thought they might run for President in 3 years? I can't think of any.
Resigning elected office is a big deal, not usually taken lightly. It's not the same as simply not running for re-election.
How many have done what she has? None, but many have resigned sometimes to run for higher office sometimes to pursue other interests. The attacks on Sarah are so outre that they beggar the imagination.