An _incentive_ to oppose I can see. But I see no duty or obligation to not do your job for 11 months just because you don't like it. Brinksmanship may be a common part of the job, but it's not in the job description.

While I believe the immediate announcements are token and positioning (the more obstinate they appear, the better the odds of a more moderate candidate) it doesn't make me LIKE it any better.