The Obama administration announced Wednesday that the No. 2 official at the Medicare agency will soon take over because Senate Republicans won’t confirm Administrator Don Berwick. Berwick’s last day will be Friday, Dec. 2.

Berwick’s principal deputy, Marilyn Tavenner, will serve as interim administrator of the Centers for Medicare and Medicaid Services (CMS) until the Senate votes on her nomination. A former secretary of health and human resources in Virginia, Tavenner is expected to be confirmed.

In a letter to colleagues at the Medicare agency, Berwick calls his decision to resign “bittersweet.”

{mosads}”Our work has been challenging, and the journey is not complete, but we are now well on our way to achieving a whole new level of security and quality for health care in America, helping not just the millions of Americans affected directly by our programs, but truly health care as a whole in our nation,” he wrote.

Tavenner has long been expected to take over after Berwick became a lightning rod for Republican anger at the healthcare reform law. A pediatrician and co-founder of the Institute for Healthcare Improvement, Berwick is well-respected throughout the healthcare industry, but his past statements of support for Great Britain’s socialized medicine system made him a target for conservatives.

President Obama nominated Berwick three times but could never get a confirmation hearing. Convinced that Berwick was the best choice to kick-start Medicare reforms under the healthcare law, Obama ended up appointing him during the July 2010 recess, which only allowed him to serve through the end of this year. 

Berwick’s fate was cemented when 42 Republican senators wrote to Obama in March to warn him they wouldn’t confirm him and urged the president to withdraw the nomination.

Tavenner has been the principal deputy administrator at CMS since February 2010 and served as acting administrator from February to July 2010.

“Before entering government service,” the administration said in a statement announcing her nomination, “Ms. Tavenner spent nearly 35 years working with healthcare providers in significantly increasing levels of responsibility, including almost 20 years in nursing, 3 years as a hospital CEO and 10 years in various senior executive level positions for Hospital Corporation of America (HCA).”

— This story was posted at 11:26 a.m. and has been updated.