Tuesday is a moment of truth for Obamacare.
It marks the final deadline for most Americans to sign up for health insurance under President Barack Obama's 2010 Affordable Care Act, popularly known as Obamacare, if they want coverage starting on Jan. 1.
If enough people - and the right mix of young and old - do not enroll, the ambitious program designed to provide health benefits to millions of uninsured and under-insured Americans risks eventually unraveling.
The deadline caps a turbulent roll-out this year for Obamacare and the HealthCare.gov website that is key to enrolling millions of people in the initiative. The website crashed upon its launch on Oct. 1, frustrating users trying to shop for insurance plans. It now is functioning much better, but is still not at 100 percent.
Despite the continuing problems, the administration is expressing confidence that Obamacare is getting back on track after enrollment accelerated in December, with more than 1 million people signing up for private insurance.
Here is a look at some notable moments in the months leading up to Obamacare's troubled launch.
EYES WIDE SHUT
In June 2012, Margaret Tavenner was worried.
As acting director of the Centers for Medicare and Medicaid Services (CMS), she was responsible for orchestrating the launch of the most sweeping U.S. domestic legislation in more than four decades.
With uncertainty surrounding how the new law would work, most states were undecided whether to establish their own insurance marketplaces or rely instead on a federally run exchange.
"What keeps me up at night is knowing around December, there are going to be like 30 states who want to come in and be state-based exchanges," Tavenner told a Washington healthcare conference, according to the Modern Healthcare newsletter.
Tavenner's anxiety - more than a year ahead of the planned launch of the exchanges - spurred concerns among industry and advocacy groups, which publicly questioned whether the multiple government agencies involved in the effort would be able to pull it off.
The White House was closely briefed on the issues. Tavenner was cleared to visit White House officials involved in the project 425 times from December 2009 to June 2013, including several meetings with Obama, visitor logs show. The White House said later that Obama knew only the broad picture, not details of the effort.
The administration also sought industry feedback, but some groups complained their warnings fell on deaf ears.
On a video of a February 2013 conference of health insurance brokers and agents in Washington, attendees could be heard grumbling when CMS official Chiquita Brooks-Lasure asked for feedback by the next day on a "streamlined" insurance application form.
The 21-page packet was jammed with questions on income and insurance status. For insurance brokers who had learned to keep it simple for customers, it was a harbinger of trouble.
"It was ridiculous," said Tom Harte, president of the National Association of Health Underwriters, which sponsored the conference. He said the group had been making suggestions to the administration on Obamacare enrollment for months.
"The image I always had (of the administration's efforts) was of a horse with blinders on, just plowing ahead and ignoring everything else," he said.
Added to technical and administrative issues, CMS had run into political problems on Capitol Hill with Tavenner's permanent appointment as director.
A former head of Virginia's state health system, Tavenner had been acting director of CMS since December 2011 while her confirmation was delayed by partisan clashes in the Senate over Obamacare. Finally, a Senate hearing was set for April 9, 2013, and she and others on the CMS staff had to prepare her for tough questions about the healthcare program's roll out.
Tavenner assured the panel that software development and testing for HealthCare.gov would be done by September 2013.
A week later, on April 18, Tavenner's boss, Katherine Sebelius, secretary of Health and Human Services, delivered a similar message to a House budget panel. She said work on the insurance exchanges was "up and running, and we are on track."
These confident public displays masked a different reality.
Earlier that month, Tavenner and Sebelius had been briefed by an outside consultant about a broad array of risks threatening the Oct. 1 launch of HealthCare.gov.
The report by the consulting firm McKinsey & Co depicted a tangled, leaderless bureaucracy managing the effort and warned of possible system failures that materialized barely six months later. It blamed tight deadlines, insufficient testing and the absence of a "single, empowered decision-making authority."
The report sounded the alarm. Attendees at high-level briefings that followed included Todd Park, the White House chief technology officer, and Brian Sivak, the HHS technology whiz brought in to jumpstart health technology systems.
The consultants met with Tavenner and Jeanne Lambrew, Obama's healthcare adviser who, two decades earlier, had worked on a failed healthcare overhaul spearheaded by then-first lady Hillary Clinton.
Obama also was briefed on McKinsey's findings, White House press secretary Jay Carney later acknowledged. White House logs show two McKinsey consultants arriving for a meeting on April 8, but the company would not comment on the visit.
The first public hints of official concern about possible problem's with Obamacare's technology actually came on March 22 - before Tavenner and Sebelius had expressed their confidence to Congress and just as McKinsey's findings began to make their way through the administration.
At a forum sponsored by America's Health Insurance Plans, the national trade association representing the health insurance industry, CMS chief technology officer Henry Chao noted that the launch of HealthCare.gov was about 200 days away.
"I'm pretty nervous - I don't know about you," Chao told the group, according to Congressional Quarterly.
"The time for debating about the size of the text on the screen, or the color, or is it a world-class user experience, that's what we used to talk about two years ago," Chao said. "Let's just make sure it's not a third-world experience."
THINGS FALL APART
By July, Chao's concerns had escalated.
A former Navy avionics technician once billed as a rising federal tech star, his reputation was tied up in the success of a website that was partially built and not yet fully tested.
His agency already had paid the website's prime contractor, CGI Federal Inc, nearly $88 million by March 2013. And costs were climbing.
Chao wrote to colleagues on July 16 to say that he feared CGI could "crash the plane at takeoff," according to e-mails released by Republican congressional investigators. CGI has declined to comment.
Alarming assessments streamed in from CMS technical advisers.
"We believe that our entire build is in jeopardy," wrote one, referring to the elaborate website construction.
E-mails flew back and forth between Chao and the contractors until a CGI vice president assured Chao, "I am on top of this."
For Chao, meeting the Oct. 1 deadline to have the website functioning well had become a matter of personal honor. Along with Tavenner, he had given sworn testimony to a congressional committee and assured skeptical members that the agency was on track.
On July 20, Chao urged his staff to redouble its effort and sent a link to his testimony.
"I wanted to share this with you so you can see and hear that both Marilyn and I, under oath, stated we are going to make Oct. 1," Chao wrote. He urged them to "put yourself in my shoes" and help him make those words the truth.
A MAD SCRAMBLE
As Oct. 1 approached, bleak assessments about the website surfaced everywhere - except from the Obama administration.
Brett Graham, a partner at the healthcare consultant Leavitt Partners, predicted a rocky enrollment period.
"The lack of testing and short timelines increases the probability of exchanges experiencing unexpected problems," he told a House subcommittee on Sept. 10.
At CMS, system tests during the third week of September were "not good and not consistent at all," one employee told Chao in an e-mail. At a time when the website should have been able to accommodate 10,000 simultaneous users, it was crashing with 500 simulated users on it - about a week before the site's scheduled launch. Contractor CGI called the glitches "part of the tuning exercise."
Chao shot off an all-caps message to his staff, ordering that tests continue, just five days before the deadline.
At the White House, technology officer Park questioned Chao about the website's progress. If Park sensed disaster, he gave no hint.
"Massive kudos again for the incredible progress the team is making!" Park wrote in an e-mail.
THE RUSH TO FIX IT
HealthCare.gov went live on Oct. 1 amid a sea of error messages, blank pages and crashed applications.
"We are making improvements as we speak," Tavenner told reporters on a conference call that afternoon.
The site's meltdown continued, however. A frustrating month of up-and-down performance prevented many Americans from purchasing insurance. The administration brought in technical advisers to help with an upgrade.
After a few weeks of stumbling explanations from top officials, Sebelius took responsibility during an Oct. 30 congressional hearing.
"No one indicated it could possibly go this wrong," she said. "Hold me accountable for the debacle."
Obama apologized on Nov. 14. Compounding the technical problems, Obama's repeated promise that Americans could keep their existing insurance if they wished proved to be inaccurate. Millions of people with bare-bones policies that did not meet the minimum standards set in the Affordable Care Act lost them.
Republican critics of Obamacare accused the administration of a lack of transparency.
"The administration was on track - on track for disaster," Rep. Fred Upton, the Republican chairman of the House Energy and Commerce Committee said on Nov. 19. "But stubbornly, they stayed the course."
The political damage flowing from the website's troubles is likely to continue through the 2014 elections. Control of Congress will be at stake, and Republicans have vowed to make Obamacare's troubled roll out, as symbolized by the botched debut of Healthcare.gov, part of an assault on the healthcare program that they say is too costly and robs Americans of coverage choices.
The website eventually found its footing.
As of late Sunday, more than 1 million people had signed up for private coverage through HealthCare.gov, and hundreds of thousands more were expected to do so Monday and Tuesday, just before a deadline to get coverage that starts Jan. 1.
Even so, the administration's initial goal of signing up 3.3 million people by the end of December seems out of reach.