When his party controlled Congress, Rep. Tom Price (R-Ga.) was a mannered backbencher, seemingly in no rush to fill the shoes of one of his predecessors in a suburban Atlanta district, the firebrand Newt Gingrich. But in the minority, the bookish physician has transformed himself into a Republican guerrilla warrior, a near-constant presence on the House floor, gumming up the works with parliamentary objections, verbal volleys and partisan maneuvering. On the flip side, Rep. Christopher H. Smith (R-N.J.) built his reputation as an uncompromising social conservative over 12 years of GOP rule. But since Democrats took control in November, he...