The point man for carrying out President Barack Obama's health care law will be stepping down after Republicans succeeded in blocking his confirmation by the Senate, the White House announced Wednesday. Medicare chief Don Berwick, a Harvard professor widely respected for his ideas on how to improve the health care system, became the most prominent casualty of the political wars over a health care overhaul whose constitutionality will be now decided by the Supreme Court.

Praising Berwick for "outstanding work," White House deputy press secretary Jamie Smith criticized Republicans for "putting political interests above the best interests of the American people." Berwick will be replaced by his principal deputy, Marilyn Tavenner, formerly Virginia's top health care official. The White House said Obama will submit Tavenner's nomination to the Senate.

Tavenner has been at Medicare since early last year, earning a reputation as a problem solver with years of real-world experience and an extensive network of industry contacts. A nurse by training, the 60-year-old Tavenner worked her way up to the senior executive ranks of a major hospital chain. She ran Virginia's health department under former Democratic Gov. Tim Kaine.