Is it possible to be sincere about a proposal that has no chance?

I was reading about John Boehner’s view of entitlement cuts, and it made me wonder about the psychology of politicians and of policy advocates. One would think that if someone has been around the block, that they could only propose legislation that has no chance for rhetorical purposes. It seems like Social Security is a sacred cow, so why would anyone propose cutting it? So is this a political strategy, or is it sincere?