Gibson Voted to Voucherize Medicare

There are no two ways about this. Gibson voted to voucherize Medicare when he was in a safe seat. But now that he has to please liberal voters in order to get reelected, Gibson conveniently changes his mind:

The 19th Congressional District Challenger Julian Schreibman is criticizing incumbent Chris Gibson for voting for Ryan's plan, which involves a complete overhaul of Medicare. The democratic challenger contends Gibson only began voting for a different proposal when redistricting created a tougher reelection battle for him.

Hard to argue with that. Gibson has never explained his about-face. What does he really believe? I thought he was supposed to be a man of principle, and not some finger-in-the-wind hack who is simply trying to hold on to his seat.