If McCain had the slightest sense of honor, dignity and ethics, he would resign his seat and give others a chance to win it. (I revere the Founders, but they made a genuine mistake in not putting Congressional term limits in the Constitution. They had entirely too much faith that people would not want to be professional politicians.)
They don't have honor, they don't trust voters, they trust themselves to tell the Governor who to appoint when they die so they have an incumbent advantage..