Kathleen Sebelius prepares to face the music on Obamacare

Health and Human Services Secretary Kathleen Sebelius – the senior Obama administration official in charge of the Affordable Care Act – gets her time in the barrel this week, appearing before a Republican-led House committee highly skeptical of (if not hostile to) the ACA, also known as "Obamacare."

GOP lawmakers (and some Democrats) demand to know why the rollout of the health-care insurance exchanges has been so rocky, with hundreds of thousands of Americans frustrated by an online sign-up system plagued by computer “glitches” that has been sketchy at best.

"The incompetence in building this website is staggering," Rep. Marsha Blackburn (R) of Tennessee, told "Fox News Sunday." Speaking Sunday on ABC’s “This Week,” Sen. John Barrasso (R) of Wyoming called Secretary Sebelius the “laughingstock of America.”

Sebelius is unlikely to be a pushover for House Republicans, some three dozen of whom have demanded that she resign over the Obamacare troubles. Politics is the family business, and she’s had plenty of experience in that rough-and-tumble world.

She was a state representative and then state insurance commissioner before serving as governor of Kansas. Her father had been the governor of Ohio, her husband is a federal magistrate judge, and her father-in-law was a US representative.

As a member of the Roman Catholic Church, she’s been publicly rebuked by senior church officials for her strong pro-choice stance on abortion.

Although Republicans in Congress grumble that she’s taken her own sweet time in getting around to facing their music – particularly since she did find time to sit down with Jon Stewart of “The Daily Show” – Sebelius already has indicated some pushback against what she sees as the highly partisan nature of the issue.

“The majority of people calling for me to resign, I would say, are people who I don't work for and who do not want this program to work in the first place,” Sebelius said this past week.

That is certainly true. It’s also true that Republican calls to “repeal and replace” the ACA – a major theme in Mitt Romney’s failed attempt to deny President Obama a second term – have yet to produce any “replace” proposal for helping millions of uninsured Americans.

Meanwhile, the administration is accentuating the positive – what positive there is.

In his radio and Internet address Saturday, Mr. Obama acknowledged that the situation “is frustrating for all of us.”

But noting that HealthCare.gov has been visited more than 20 million times and that nearly 700,000 people have applied for coverage through the insurance exchanges since Oct. 1, he said, “We’ve got people working overtime, 24/7, to boost capacity and address these problems, every single day.”

In a blog post Saturday, Sebelius pointed to some new numbers indicating that “by the end of November, HealthCare.gov will work smoothly for the vast majority of consumers.”

Sebelius praised the performance of the “data hub,” which connects to the Social Security Administration and Internal Revenue Service (IRS) to verify applicants' identity and income.

She said it took the hub less than 1.2 seconds to route information, and called it "a model of efficiency and security."

Sebelius said the Social Security Administration has been pinged by the data hub more than 4.2 million times as individuals or households try to establish an account using a Social Security number, with the biggest numbers coming from Pennsylvania, New York, California, West Virginia, and Washington.

The IRS has handled more than 1.3 million requests to verify income and family size tax data from the hub – about 80,000 requests per day – and has been able to provide responses through the hub in less than a second, on average, Sebelius said.

The IRS has also fulfilled more than 330,000 requests for a "computation service" that determines whether someone is eligible for subsidies based on their income, she said.

"The hub is on the job, and so are we," said Sebelius,

Such figures and upbeat assertions are unlikely to satisfy House Republicans who’ll be grilling Sebelius this week. But at least one Republican elected official sympathizes with the HHS secretary.

The man who now holds one of Sebelius’s former jobs says the glitches in the rollout of Obamacare are not her fault.

"The complexity of what she's having to deal with is massive and in an environment that's been pretty politically charged, to say the least. So I have a great deal of sympathy for what she's having to work through," Kansas Insurance Commissioner Sandy Praeger told NPR. "I know she's probably very frustrated."

This report includes material from Reuters.