HHS Secretary Kathleen Sebelius seemed to have weathered the maelstrom surrounding the botched rollout of the government's health insurance exchanges back in October and come through the other side where more than 7 million people signed up for health insurance through the exchanges.

But on Thursday, after five years at the HHS helm, Sebelius resigned.

President Barack Obama is set to nominate Sylvia Mathews Burwell, director of the White House Office of Management and Budget, to take over at HHS. She faces congressional confirmation -- where, according to pundits, she is likely to face resistance from Republican senators who continue to oppose the Affordable Care Act.

Back in October the launch of the HealthCare.gov website left people who wanted to sign up unable to do so, with the website apparently unable to handle the rush of applicants. Several Republicans called for Sebelius' resignation and took the opportunity to criticize Obamacare, their name for the ACA.

Even as recently as April 1 when the Senate approved a patch for the Sustainable Growth Rate, or SGR formula for Medicare payments to physicians, in lieu of providing a permanent fix, several senators put forward measures to do away with the ACA.

When the House Committee on Energy and Commerce summoned Sebelius to Capitol Hill on Oct. 30, to answer questions about HealthCare.gov, she told the panel the website "has not lived up to the expectations of the American people and is not acceptable. We are committed to fixing these problems as soon as possible."

Asked who was responsible for the website breakdown, Sebelius responded, "Hold me accountable for the debacle. I'm responsible."

Soon after, government contractors who had worked on the site were fired.

By December, the White House was reporting that the website was much-improved -- "like night and day."

"Root causes of the problems included hundreds of software bugs, inadequate hardware infrastructure and a general lack of system monitoring. The staff also identified weaknesses in how the site was being managed," Jeff Zients, management expert and advisor to CMS and HHS, said on Dec. 1.