There is a new job opening up for the next key Obamacare official that heads the Centers for Medicare and Medicaid Services (CMS).

Marilyn Tavenner announced Friday that she would be stepping down from her job that effects more than 100 million American lives through its coverage plans and initiatives. As the head of CMS she was responsible for overseeing more than a trillion dollars in annual spending and played a major role in implementing the Affordable Care Act. 

It's an understatement to say the head of CMS is a huge, politically sensitive job. And that could be why there is such a big turnover in officials holding the position. 

Andy Slavitt, who will be replacing Tavenner on Feb. 1, will be the 14th person since 2000 to serve as head of CMS in some capacity, reported Forbes. Slavitt is currently her principal deputy.

Don Berwick, who served just 18 months as the CMS administrator, held the position before Tavenner. 

Tavenner will be most remembered for her role in the implementation of the Affordable Care Act. She helped develop  HealthCare.gov, the Obamacare insurance-shopping website that launched and promptly crashed on Oct. 1, 2013. Tavenner faced harsh criticism after that, as the website essentially was nonfunctional for nearly two months. The crash created a severe political crisis for the Obama administration and almost ruined the whole health plan all together. 

Aside from the major Obamacare website issue, Tavenner will also be remembered for several successes from her time in office.

She is also responsible for Obamacare exchanges' strong enrollment numbers, the decline in the nation's uninsured rate, the government's ongoing work to improve health care quality, and the ongoing slowdown in Medicare spending. 

"Marilyn Tavenner has devoted five years and countless hours to the cause of improving health care quality, holding down costs, protecting the Medicare Trust Fund and expanding access to affordable health care coverage to millions of Americans," HHS Secretary Burwell said in a statement scheduled to be released Friday. "In so doing, she delivered historic results that have impacted countless lives - both today and for decades to come - all for the better."