As the healthcare overhaul heads to the Senate floor, Senator Tom Coburn, a family practice physician, is preparing for what he considers a career pinnacle of havoc. Enacting the proposal, he said, would be catastrophic, and so if precedent holds, he will try to hinder it with every annoying tool in his arsenal: filing amendments, undertaking filibusters, and objecting strenuously. To Coburn, charges of obstructionism are a mark of honor he will wear as proudly as ever in the coming weeks.