President Obama accepted her resignation this week and will nominate Sylvia Mathews Burwell, the director of the Office of Management and Budget, to take her place:
The departure comes as the Obama administration tries to move beyond its early stumbles in carrying out the law, persuade a still-skeptical public of its lasting benefits, and help Democratic incumbents, who face blistering attack ads after supporting the legislation, survive the midterm elections this fall.
Officials said Ms. Sebelius, 65, made the decision to resign and was not forced out. But the frustration at the White House over her performance had become increasingly clear, as administration aides worried that the crippling problems at HealthCare.gov, the website set up to enroll Americans in insurance exchanges, would result in lasting damage to the president’s legacy.
Even last week, as Mr. Obama triumphantly announced that enrollments in the exchanges had exceeded seven million, she did not appear next to him for the news conference in the Rose Garden.
The president is hoping that Ms. Burwell, 48, a Harvard- and Oxford-educated West Virginia native with a background in economic policy, will bring an intense focus and management acumen to the department. The budget office, which she has overseen since April of last year, is deeply involved in developing and carrying out health care policy.
"The president wants to make sure we have a proven manager and relentless implementer in the job over there, which is why he is going to nominate Sylvia," said Denis R. McDonough, the White House chief of staff.