Mark McClellan, who oversaw the biggest change in Medicare since its inception, said Tuesday he is resigning and will likely go work for a think tank.
No replacement was immediately named, although White House press secretary Tony Snow said McClellan had made it known for some time that he intended to leave.
"He'll be missed by the president and the entire administration," Snow said. "The president has the highest regard for Mark McClellan and appreciates the work he's done for the administration."
McClellan, a physician and economist, was one of President Bush's economic advisers and served as the Food and Drug Administration commissioner before he was tapped in 2004 to administer the Medicare and Medicaid programs. He also worked in the Clinton administration at the Treasury Department.
His main task over the past year was to get the new Medicare drug program up and running. The program got off to a rocky start, and states had to step in to ensure that the poorest of beneficiaries could continue to get their medicine. Service and care has improved markedly in past months and analysts say McClellan was responsible for much of that turnaround.
McClellan told The Associated Press that he will leave the agency in about five weeks and that he would likely work for a think tank where he could do more writing about how to make health care better in the United States.
"My kids don't remember me in a job where I got home regularly for dinner. It's just time," said McClellan, the father of 7-year-old twin girls. "We've gotten a lot accomplished and I'm very confident with the track the agency is on."
As the administrator at CMS, McClellan oversaw programs serving more than 80 million Americans at a cost of about $570 billion annually. But it was the start of a drug benefit under Medicare that was his biggest priority over the past two years. Under the program, elderly beneficiaries enroll in plans administered by private insurers. Seniors had dozens upon dozens of plans to pick from, leaving many of them confused and frustrated.
However, officials say the program will save the average beneficiary about $1,100. Complaints have dropped significantly. Independent polling shows that the large majority of those who enroll are satisfied with their coverage.
"We've found and fixed startup problems, we are delivering coverage at a cost at least 25 percent less than had been expected, and we are seeing beneficiary satisfaction rates of over 80 percent," he told his staff in an e-mail Tuesday morning.
McClellan is the brother of former White House press secretary Scott McClellan. His mother, Carole Keeton Strayhorn, is the Texas comptroller and is running for governor as an independent.