The architect of the GOP’s controversial Medicare overhaul delivered a forceful defense of the plan here Monday, saying it would empower seniors and accusing President Obama of having a “shared-scarcity mentality” that promotes “bureaucratically rationed health care.”

Facing a backlash from voters over his proposal to turn Medicare into a system that subsidizes health-care coverage for retirees on the private market, House Budget Chairman Paul Ryan (Wis.) moved to recast the plan as the only one that would make the economy grow.