"You don't know how people are going to react," Mendelson says. "You didn't know, for example, whether employers would react by dropping onto the exchange. You didn't know that the Obama administration would extend grandfathered plans for another year, and that would mean lower enrollment. There was just a lot that wasn't known."

Aside from those three expansions — none of which were a perfect analogy to Obamacare — there just wasn't much information to go off.

There was the Children's Health Insurance Program, which gave millions of low-income kids the opportunity to gain coverage in 1995. Medicare Part D, which allowed seniors to enroll in drug coverage, was another data point. Lastly, there was Massachusetts' universal coverage plan that launched in 2006.

Forecasters relied on a sparse set of information when they gamed out how many people would sign up for Obamacare. They mostly looked at three, smaller insurance expansions that could at least give some measure of what to expect with the larger health reform law.

"These are all educated guesses," says Dan Mendelson, president of the research company Avalere Health. "We did our own estimates for clients, and also came up with the 7 million number, but also put a plus or minus of 20 to 30 percent around it."

The previous updates were typically posted with little fanfare — and the agency's three-page document, "CBO's February 2013 Estimate of the Effects of the Affordable Care Act on Health Insurance Coverage ," looked just as dull as the last few forecasts. Just like the prior report, it was an estimate couched in caveats and qualifications of how many people would use the health law's marketplace in its first year.

The CBO had published four previous estimates of how many people would enroll in coverage through the new exchanges. The number would bounce around by 1 or 2 million, depending on how the agency tweaked its model.

The Congressional Budget Office didn't realize it was drawing a political line in the sand when, in February 2013, it quietly projected that 7 million people would enroll in health insurance coverage through the new health exchanges.

Forecasters had little information to go off when they estimated last winter how many people would sign up for Obamacare.

Behind the scenes, convincing Americans that they could afford insurance was the White House's biggest challenge in making Obamacare work.

Importantly, the success of Obamacare's first enrollment period — as told in interviews with Obama administration officials, advocacy groups, health care experts, and Obamacare shoppers — was not just about fixing a broken website. Healthcare.gov's disastrous rollout and ultimate repair mattered, but they didn't explain why people decided to buy insurance.

The story of how the White House got 8 million people to sign up for health insurance is largely about people like Maluf. Obamacare hit its enrollment target because it was selling something that at least 8 million people wanted: affordable health insurance.

"It's been very challenging," Maluf says. "I haven't been able to travel much. I really don't have any money left to spare now."

Maluf ultimately decided, after three months of deliberation, to purchase an insurance plan. That meant trade-offs: she's skipping a trip to Brazil to visit her baby niece, and putting off building a website to advertise her pilates business.

"I went back and forth and back and forth, on what I should do," she says. "The whole October and November and December, I was going back and forth. On Christmas Eve, I made my decision."

Maluf didn't expect to have high medical bills; she's the type of person who gets one or two colds each year. In the nine years she spent without coverage, she never had a major illness.

Maluf was optimistic about the health care law when it passed in 2010; she hoped it would lower her premiums to about $200, an amount she thought she could fit into her budget. Instead, the insurance plan would cost $359 after a subsidy. It was much less than the premiums she saw in the past, but nearly double what she'd hoped to pay.

Health policy experts do know that higher enrollment tends to be better for any insurance program. When more people are signing up for health insurance, it's more likely to include a number of healthier and younger Americans — the people who have the lowest health insurance costs. A small pool of enrollees, on the other hand, typically indicates that only the sick and elderly — the people who really need insurance — actually decided to sign up.

"A bigger risk pool is almost always a healthier risk pool," Kaiser Family Foundation's Larry Levitt says. "As you increase enrollment, you're reaching more and more of the healthier groups, and that will improve the risk pool. "

Higher enrollment would also be a mark of policy success in a different way: it would mean the president's signature domestic policy accomplishment had affected a greater number of Americans and more greatly reduced the ranks of the 48 million who lack coverage.

Seven million enrollments though, wasn't the magical number where those policy successes happened. There's not much different about an insurance risk pool that covers 6.8 million people or one with 7.2 million members.

In Washington, though, politicians aren't in the market for uncertainty; they wanted a particular figure they could point to, the yardstick to judge the health care law's success or failure. And so seven million quickly became the number that, if Obamacare was to be considered a political success in 2014, the White House would have to hit.

"The administration would need to enroll 68,000 per day to meet their year-end goal," Ways and Means Chairman Dave Camp (R-Mich.) said in a November statement.

At that point, Obamacare wasn't going very well: it was signing up an average of 3,400 people each day.

In October and November of last year, Anne Filipic thought a lot about the Serenity Prayer: "God grant me the serenity to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference."

Filipic was running the country's largest Obamacare outreach group, Enroll America. Health law advocates had founded the group with the express purpose of maximizing enrollment in the health care law's new programs. But in October and November, it was nearly impossible for her group — or any other — to sign up people for insurance coverage.

Last fall, instead of selling insurance plans, Healthcare.gov mostly delivered error messages and long wait times. Applications would get lost and stalled, and some shoppers reported making at least 20 attempts at purchasing coverage in October, all to no avail.

Healthcare.gov's terrible rollout made regular appearances on newspaper front pages and in White House press briefings. "From the start, signs of trouble at health portal," a New York Times headline on October 12 read. "Obamacare's balky website endangers its launch," the Washington Post editorial board opined the same day.

"We were frustrated," Filipic says. "We were incredibly frustrated."

This wasn't the problem that the Obamacare supporters had prepared for. They had initially expected to spend the fall convincing uninsured Americans that health insurance coverage was a good deal. They didn't expect two months where the website that could show consumers how much they would pay would barely function.

The federal government held tense calls with outreach groups. Multiple times per week in October, advocates would get on the conference call to tell Centers for Medicare and Medicaid Services officials about what wasn't working.

"There were moments when people at HHS would be like, ‘Dammit, I wish I knew how to program!'" says Jen Beeson, who directs government affairs at pro-health law group Families USA. "It was really frustrating and it was like, well, you weren't hired to be a programmer. You were hired to be a spokesperson."

Enroll America, Families USA, and other groups running major outreach campaigns did the best they could without a website to enroll shoppers in coverage. They collected email addresses, held outreach sessions, and kept knocking on doors. They worked on the assumption that, at some point, the website would be fixed, and they could make better use of all the names and emails and phone numbers they had stockpiled.

"We really used that time to continue to organize," Filipic says. "That was when we started to do what we had originally conceived of as enrollment events. We didn't cancel them, but started use them as more educational and informational events."

While media attention focused on Healthcare.gov, two pollsters were realizing that Obamacare's problems ran even deeper than a broken website. Tresa Undem and Michael Perry run their own polling firm PerryUndem, which has done significant survey work for health law advocates. They had spent months criss-crossing the country, hosting focus groups and surveying the uninsured about the health care law.

They had good news and not-so-good news for health law advocates. The good news: the avalanche of negative stories about Healthcare.gov hadn't actually scared people off from using the website. Most of the people eligible to shop on the site hadn't even bothered to try it yet.

"The dialogue in the media hadn't filtered down, to a degree," Perry says. "People were putting stuff off, and planning to do it later. So from what we could see, the glitches weren't having any significant effect. That was the encouraging thing we were able to tell the outreach groups we talked to, that there was no lasting damage done."

But their research also found one big problem, arguably a bigger obstacle than a dysfunctional website. The vast majority of the people Perry and Undem surveyed thought health insurance was way too expensive; they had no idea that the federal government would provide subsidies to many low- and middle-income Americans.

These were people who said yes, they did want health insurance, but they weren't going to bother to shop for it.

"There's one woman we talked to, who I remember very clearly saying, ‘If you don't have money for shoes, you don't go shoe shopping,'" Undem says of the focus groups. "That's when we learned that 69 percent hadn't heard about financial help. If you don't know about financial help, and affordability is the number one concern, that's a huge problem."

"It seemed like everyone's head was spinning. The first three months were fast and furious and mostly negative."

This wasn't a total surprise to the health care community. Survey after survey finds cost to be a huge barrier to health insurance coverage. In one survey, the Kaiser Family Foundation found only 1.5 percent of the uninsured said they didn't want insurance. Another 61 percent said they lacked coverage because they lost their job or the cost was too high.

What was different about Undem and Perry's research is that they were finding, for the first time during the open enrollment period, that shoppers had no clue that in many cases that large barrier had come down and they qualified for financial help with their premiums.

Undem and Perry presented their research to a team of White House officials the week before Christmas, shortly after Healthcare.gov had begun working reliably, and briefed then-Health and Human Services Secretary Kathleen Sebelius in mid-January.

"It seemed like everyone's head was spinning," Undem recalls of the White House meeting. "The first three months were fast and furious and mostly negative. So it was just a lot of nervousness and anxiousness."

Undem and Perry had two main points that were at the top of the one-page document they handed out to White House staffers.

"These glitches are not as big of a problem as you might think," Undem remembers telling the group. "People keep going back and back. The number two point was, people don't know that they can get financial help. There are big information gaps that haven't been filled in."

The White House had a task ahead of it arguably bigger than fixing Healthcare.gov: it had three short months to convince Americans that the health insurance it was selling was actually a good deal.

There was one big difference between the uninsured people who signed up for Obamacare and those who didn't: they knew more about the health care law, especially about the financial help.

Fifty-six percent of those who signed up for plans this year knew about the subsidies available to low- and middle-income Americans, compared to 26 percent of those who did not enroll, according to Perry and Undem's post-enrollment survey work, which was sponsored by Enroll America.

White House and pro-Obamacare groups did two things differently at the end of open enrollment, both aimed at increasing these numbers: they increased the number of events they hosted and overhauled their consumer message to make it all about financial help.

Obama administration officials did more than 300 radio interviews during the final six weeks of open enrollment, focusing on radio stations that reach young adults, Hispanics, and African Americans. Nearly everybody in the upper echelons of White House management pitched in, although some more than others — senior advisor Valerie Jarrett, for example, logged more than 80 appearances.

The law's supporters didn't know it at the time, but later consumer research showed that the awareness effort was making inroads: the Obama administration estimates that 95 percent of young adults, for example, were reached by their television and radio ads. Among that population of uninsured 18- to 34-year-olds, two-thirds visited healthcare.gov and half reported shopping for coverage.

"Our enrollment activity doubled from February to March," says Julie Bataille, who runs the office of communications at the Center for Medicare and Medicaid Services. "By the end of the month, people were making appointments and waiting in line."

The Obama administration began to add a tagline to all of its advertisements, meant to encourage people to sign up soon. Any paid marketing effort after February would end with "Don't wait, sign up by March 31" or "enrollment ends March 31."

Enrollment groups had doubled down on Perry and Undem's research, focusing their message on financial assistance during the final push. Enroll America added a subsidy calculator to its website in February, it quickly became the most-clicked on part of the entire site. They found that, when they sent out emails with a subject line about financial help, more people would actually click on the message and open it.

The allure of low prices seemed to motivate the people who showed up at in-person enrollment events, too.

"I will never forget one woman who came to one of our events to get enrolled, and found out her monthly premium was going to be $3," says Alethia Henry, who ran Planned Parenthood's outreach program. "She said, ‘Hold on, wait a minute, I'm going to go get my sister.' And she actually left our event and came back with her sister."

The individual mandate that requires the vast majority of Americans to carry health insurance coverage also seems to have played a significant role, although it wasn't as heavily emphasized by enrollment groups. When Enroll America surveyed Obamacare buyers on the reasons they purchased a plan, the most frequent response they got back was "because its the law."

The Obama administration's daily data on Obamacare activity — information on enrollment, online traffic, call center volume and other metrics — had a recognizable ebb and flow to to it by late February. The first two weeks of any month tended to have more activity than the second two weeks, which seemed to reflect people signing up before the regular deadline on the 15th to buy coverage that would start the first day of the next month.

"There's one woman we talked to, who I remember very clearly saying, ‘If you don't have money for shoes, you don't go shoe shopping.'"

And each week had its own pattern, too. Monday would be a relatively slow day, followed by slightly traffic and sign-ups on Tuesday. The pace would pick-up more on Wednesday and hit a peak on Thursday, before tapering off on the weekend.

February 28 was a Friday at the end of the month. All available data suggested that this was the exact moment when enrollment activity would fall to a lull. That didn't happen: healthcare.gov activity was actually higher than days prior.

"The final week of February was a good insight into what was about to happen," one senior administration official familiar with the regular reports said. "We did not see the big, dramatic last-week drop off that we had seen in previous months. Once we saw that it was like, you know what, this is going to be a monster month."

The story of Obamacare's first open enrollment period is only one chapter in a longer narrative. The next chapter will have a slight plot twist: whether the people who thought insurance was a good deal decide to renew their plans in 2014 — and if those who sat out the first shopping season give Obamacare a second look.

While there are 8 million Americans who thought the health plans in Obamacare were a good deal, the Kaiser Family Foundation estimates there are 20 million more who decided not to sign up. For many of them, the existing prices were too high. The Enroll America survey found that 39 percent of shoppers who didn't buy coverage said "the costs aren't worth it" in explaining their decision. It came up more frequently than any other explanation.

"Eight million people clearly found it affordable, but there are millions more that didn't buy," says Kaiser Family Foundation's Levitt. "The test for affordability is how many people enroll next year, and the year after."

Maluf says she does want to buy her health plan, which she hasn't used yet, again next year. But she's not totally sure she will be able to afford it anymore. The rent on both her apartment and her pilates studio increased by more than $200, which has further squeezed her budget. She thinks her income this year, which she earns at individual pilates lessons and therapy sessions, will be lower than she had initially expected.

"I am at the maximum," says Maluf of what she currently pays for health coverage. "I couldn't go higher than this, not by a penny."

Maluf describes herself as an optimist though, and likes to hope that, by this time next year, her premium won't be a problem. "Hopefully," she says, "things will get better and better and $359 will be a breeze."