"This is like trying to find a parking spot at Wal-Mart on Dec. 23," said Jason Stevenson, working with a Utah nonprofit group helping people enroll.
At times, more than 125,000 people were simultaneously using HealthCare.gov, straining it beyond its capacity. For long stretches Monday, applicants were shuttled to a virtual waiting room where they could leave an email address and be contacted later.
Officials said the site had not crashed but was experiencing very heavy volume. The website, which was receiving 1.5 million visitors a day last week, had recorded about 2 million through 3 p.m. EDT. Call centers have more than 840,000 calls.
Supporters of the health care law fanned out across the country in a final dash to sign up uninsured Americans. People not signed up for health insurance by the deadline, either through their jobs or on their own, were subject to being fined by the IRS, and that threat was helping drive the final dash.
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The administration announced last week that people still in line by midnight would get extra time to enroll.
The website stumbled early in the day — out of service for nearly four hours as technicians patched a software bug. Another hiccup in early afternoon temporarily kept new applicants from signing up, and then things slowed further. Overwhelmed by computer problems when launched last fall, the system has been working much better in recent months, but independent testers say it still runs slowly.
At Chicago's Norwegian American Hospital, people began lining up shortly after 7 a.m. to get help signing up for subsidized private health insurance.
Lucy Martinez, an unemployed single mother of two boys, said she'd previously tried to enroll at a clinic in another part of the city but there was always a problem. She'd wait and wait and they wouldn't call her name, or they would ask her for paperwork that she was told earlier she didn't need, she said. Her diabetic mother would start sweating so they'd have to leave.
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She's heard "that this would be better here," said Martinez, adding that her mother successfully signed up Sunday at a different location.
At St. Francis Hospital in Wilmington, Del., enrollment counselor Hubert Worthen plunged into a long day. "I got my energy drink," he said. "This is epic, man."
At a Houston community center, there were immigrants from Ethiopia, Nepal, Eritrea, Somalia, Iraq, Iran and other conflict-torn areas, many of them trying anew after failing to complete applications previously. In addition to needing help with the actual enrollment, they needed to wait for interpreters. Many had taken a day off from work, hoping to meet the deadline.
The White House and other supporters of the law were hoping for an enrollment surge that would confound skeptics.