Embattled Obamacare czar Kathleen Sebelius finally takes the hot seat before Congress on Wednesday to answer questions about the botched launch of HealthCare.gov.
The House Energy and Commerce Committee said it wants Sebelius, secretary of Health and Human Services, to help members fully understand the failures of the federally run health insurance marketplace and "who is responsible" for the troubled website.
Since its introduction Oct. 1, HeathCare.gov has run slowly, if at all, because of software problems that have crippled enrollment in insurance plans for residents of 36 states and led to errors in the enrollment data sent to insurers.
The debacle prompted the White House to enlist management expert Jeff Zients to oversee a frantic effort to fix the site.
Here are the questions committee members should ask Sebelius—repeatedly if necessary—about HealthCare.gov.
(Read more: Was Sebelius warned of Obamacare Web site train wreck? No comment.)
1. What did you know, when did you know it, and who told you?
Sebelius and HHS have been vague at best about who exactly told Sebelius the website had software problems. The glitches became apparent in testing just two weeks or so before launch.
Contractors who worked on the site testified last week that the testing was delayed until the late date at the direction of the Centers for Medicare and Medicaid Services (CMS), the HHS division that runs HealthCare.gov.
Committee members are likely to press Sebelius on why that testing was not done sooner so that the problems it exposed might have been fixed or largely addressed before the launch.
2. Did you ever consider not launching Oct. 1?
Sebelius has claimed that HealthCare.gov had to open to the public by that date, but that assertion has been challenged by some who said she had the discretion to delay.
Critics have said that given the software problems uncovered in the last-minute testing, the secretary—and the goal of enrolling up to 7 million people in Obamacare insurance by March—would have been better served by delaying the rollout to sort out those issues and not address them on the fly.
Technology experts and others have suggested that HealthCare.gov should have been phased in one state or group of states at a time, to see how the system worked on a smaller scale and make fixes along the way. HHS also could have phased in parts of the site, letting customers shop for plans weeks before they were required to create accounts and apply for coverage.
(Read more: HealthCare.gov fixable by late November: Obama official)
HealthCare.gov's problems are said to stem at least partly from the requirement that users create accounts before seeing the prices they would actually pay, as opposed to estimates.
3. Why has no one been fired?
When it became clear that HealthCare.gov had serious problems—ones that were being downplayed in HHS's initial comments after Oct. 1—a number of Republican opponents of Obamacare began demanding that Sebelius resign.
She has adamantly resisted those calls for her head and has been supported by the White House, which doesn't want to look weak in the face of GOP criticism, and which would also find it difficult if not impossible to get a successor for Sebelius confirmed because of acrimony over the law on Capitol Hill.
But Sebelius, HHS, and CMS also have rebuffed calls that anyone below Sebelius be fired, including CMS chief Marilyn Tavenner, whose HHS division has taken responsibility for the launch and running of HealthCare.gov.
(Read more: Medicare chief: Sorry about that)
It was CMS' job to coordinate site components, which were developed by individual contractors, and to ensure they worked together properly as designed. They clearly haven't.
At the same time, HHS has not said whether it will seek rebates from contractors because of problems with the quality of their work.
4. What does all this cost?
Figuring the total cost of creating and launching HealthCare.gov has been tough for the media. By looking at data about individual contractors, it's obvious that the costs to date have been in the hundreds of millions of dollars. But getting a firm number has been tricky.
Her department also has not given a precise price tag for fixing HealthCare.gov. In a call with reporters last week, a CMS spokeswoman said that the UnitedHealth Group subsidiary QSSI, which had just been appointed general contractor for the repair effort, would be paid under an existing contract but did not specify how much that was.
5. What contingency plans do you have?
Many Republicans and some Democrats on Capitol Hill have increasingly called for a one-year suspension of the so-called individual mandate, which requires nearly all Americans to obtain health insurance by March or face a tax penalty.
Those members have said the mandate should be delayed because many people have been unable to enroll. At the same time, millions of people are receiving cancellation notices from their insurers, which say the old plans don't meet Affordable Care Act standards.
HHS has not acknowledged even considering a one-year delay of that mandate, saying that the site will be fixed by late November and that it expects people to be able use it to to enroll in coverage that begins Jan. 1. But if troubles persist, there will likely be more calls for a one-year delay, or for at least an extension of the open enrollment period beyond March 31.
It is likely that Sebelius will stand firm on not granting any delay.
(Read more: The GOP's Obamacare expert?)
6. What are the enrollment numbers?
Each day since the Oct. 1 launch, HHS has been repeatedly asked and has refused to answer how many people have signed up for coverage through HealthCare.gov.
Sebelius—and Tavenner, as recently as Tuesday, in testimony to Congress—has said that enrollment numbers will be released next month.
HHS' stance suggests that it has little good to say about current levels of enrollment.
Tavenner told Congress on Tuesday, "We expect the initial number to be small." Insurers have also indicated they are seeing relatively low enrollment via HealthCare.gov.
A number of states have been issuing regular updates on their enrollment levels on their state-run health exchanges.
—By CNBC's Dan Mangan. Follow him on Twitter @_DanMangan