President Obama accepted Health and Human Services Secretary Kathleen Sebelius' resignation earlier this week and will nominate Sylvia Mathews Burwell, director of the Office of Management and Budget, to replace her Friday morning in an attempt to turn the page on the tumultuous beginning of the president's signature health care law.

The news came Thursday evening nearly six months after the problem-riddled fall Obamacare rollout and just hours after Sebelius, 65, testified before a Senate committee that enrollment in the federal insurance exchanges had reached 7.5 million by the March 31 deadline.

That figure exceeded the administration's original goal, which Obama celebrated last week with a combative speech saying that Americans supported and have faith in the law even after Republicans spent the last year running negative attack ads trying to undermine it.

Despite the better-than-expected enrollment numbers, negative public perceptions of the health care law and the bungled rollout have persisted, with polls showing a majority of Americans maintain a negative view. A USA Today/Pew Research survey taken last week showed 39.8 percent in favor of the law and 52.2 percent in opposition.

Sebelius' departure signals the administration's desire to make a clean break from its early stumbles and mistakes and focus on following through on implementing the law in what they hope will be a more steady and deliberate manner. It also gives vulnerable Democrats, already facing sharp attacks ads in their tight re-election races, evidence to point to that the administration has turned the corner on the Obamacare problems and has a fresh new leader at the helm.

Burwell, 48, a Harvard-educated West Virginia native and Rhodes scholar, was confirmed as Obama's budget director on a 96-0 Senate vote nearly a year ago. Low-key and unassuming, the former Clinton administration official is known as a straight-shooter and an effective manager of the White House's budget arm, which is enmeshed in carrying out the health care policy.

Supporters say she has a gift for playing down controversy and doesn't crave the spotlight. In fact, after serving as White House deputy chief of staff and chief of staff to then-Treasury Secretary Robert Rubin and deputy OMB director under Lew, she left Washington and moved to Seattle to work at the Bill and Melinda Gates Foundation and later continued to work on the philanthropic side of the corporate world at the Walmart Foundation.

Obama coaxed Burwell back to the beltway last year to take over OMB after her predecessor, Jack Lew, left. She was at ground zero of the government showdown but managed to attract very few headlines. In contrast, Lew, who served two years in the post before becoming Obama's chief of staff and then Treasury secretary, often showed up at White House press conferences and was a regular on the political talk-show circuit.

Burwell's ability to rise above the blistering partisan pray will be tested immediately as she attempts to persuade a skeptical public that Obamacare is on a smoother path and won't create more uncertainty and chaos for patients, doctors, hospitals and insurers alike.

She is all but guaranteed Senate confirmation under a rule change put in place late last year by Senate Majority Leader Harry Reid, D-Nev., that allows a straight majority vote on all presidential nominations.

But Burwell will be forced to confront an onslaught of questions about the law's future from Republicans as well as Democrats angered over the disastrous rollout's impact on their re-election chances. Americans want to know how many enrollees have actually paid their premiums, whether more people will lose the plans they had and liked, and whether premiums and deductibles will continue to shoot up in the months ahead.

Although they are unlikely to block her confirmation, Senate Republicans are already promising to put Burwell through the paces.

“... She inherits a very, very difficult task and she's going to have a tough road ahead of her in terms of securing the Senate confirmation, especially if she is not prepared to answer all kinds of questions about how independent she's willing to be and how open and transparent she's willing to be with Congress," Sen. Mike Lee, R-Utah, a conservative stalwart who pushed hard to defund Obamacare last year, told Fox News' Greta Van Susteren Thursday night.

Even in the post-nuclear Senate, Lee predicted Burwell will face a serious grilling from both Republicans and Democrats who are taking the heat for the the law's rocky beginning.

Sen. Chuck Grassley, an Iowa Republican and the ranking member of the Judiciary Committee, said in many ways, anyone put in charge of Obamacare was set up to fail because the law is so “unready, poorly structured and unpopular.”

“She was given a law that was just about written in pencil the way the deadlines changed all the time,” he said in a statement. “That put her in a position of having a strained relationship with Congress.”

Grassley also said the White House cannot simply erase the ongoing problems with the law by putting someone new in charge.

“It’s disingenuous for the White House to distance itself from the problems and attribute them to partisan sniping at one member of the administration,” he said. “The next secretary might have a fresh start with the public and Congress but the flawed law is still the law.”

Sen. Orrin Hatch, a Utah Republican and the ranking member of the Senate Finance Committee, was more charitable, saying that Sebelius had one of the toughest jobs in Washington, implementing a flawed law “that continues to fall woefully short of its promises to the American people.”

“While we haven’t always agreed, Secretary Sebelius did the best she could during the tumultuous and volatile rollout of the law,” he said. “I thank her for her service and wish her and her family all the best in their future endeavors.”

House Minority Leader Nancy Pelosi, D-Calif., who worked directly with Sebelius in pushing the law through Congress when Democrats controlled the majority in both chambers in 2010, has stood by the law and Sebelius throughout the failed rollout.

After Sebelius' resignation was announced, Pelosi had nothing but praise for her long tenure at HHS and record on implementing Obamacare and thanked her for her “extraordinary service.”

“From day one, Secretary Sebelius has remained laser-focused on a single purpose: to make health care a right, not a privilege, for all Americans. Her leadership has been forceful, effective, and essential,” she said in a statement.