He can remain on the ballot - but announce that he is suspending his campaign and asking his supporters to vote for Arnold.
This would allow him to keep his word while ensuring that Bustamante does not get elected.
Why? His mere presence is adding a voter passion and focus to this race which I have not seen in years. As long as there is fear that Busty may win - I take Grey's sudden loss of a job as a given, because if it ISN'T I'm gonna pop a cork - people will continue to bring up his racism, his illegal donations which he won't return, his continued Prop 54 ads which are STILL financed with that illegal money which he refuses to return and his promise to raise taxes.