Jammed phone lines and unreliable websites failed to stop a last-minute rush by hundreds of thousands of Americans trying to sign up for health coverage under President Barack Obama's signature domestic policy initiative.
But it is unclear how well the Affordable Care Act will work and whether its implementation will see Americans change their views on a law that remains unpopular and widely misunderstood.
Government officials told The Associated Press late Monday (local time) that they were on track to sign up more than 7 million Americans for health insurance by the deadline on midnight Monday.
The 7 million target, thought to be out of reach by most experts, was reached on a day that saw surging consumer interest as well as vexing computer glitches that slowed sign-ups on the HealthCare.gov website.
A government official told The Associated Press that the 7 million mark had been crossed. The official spoke on condition of anonymity because the official was not authorised to discuss developments by name before Obama's announcement.
About 50 million Americans lacked health care coverage as the law began taking effect, and supporters hope it will significantly reduce the ranks of the uninsured.
But the administration has not said how many of those who already have signed up closed the deal by paying their first month's premiums. Also unknown is how many were previously uninsured - the real test of Obama's health care overhaul. In addition, the law expands coverage for low-income people through Medicaid, the government health care program for the poor, but only about half the states have agreed to implement that option.
The months ahead will show whether the Affordable Care Act will meet its mandate to provide affordable health care coverage or whether high deductibles, paperwork snags and narrow physician networks make it a bust.
The 2010 passage of the Affordable Care Act has been the No 1 legislative achievement of Obama's presidency.
Eager to deny Obama any kind of legislative legacy, Republicans have bitterly opposed the law which they say swells big government and represents an unprecedented federal intrusion in the US economy.
After winning control of the House of Representatives in the 2010 elections, Republicans have voted more than 50 times to revoke or seriously undermine the program, widely known as "Obamacare." Those bills have never made it to the floor in the Democratic-controlled Senate.
House Speaker John Boehner said Monday that Republican lawmakers remain committed to repealing Obama's law.
Since the initial enrolment period began in October, millions of Americans have signed up for health insurance through the state and federal exchanges, with many of the policies heavily subsidised to make them affordable for lower -and-middle income Americans.
On Monday, supporters of the health care law fanned out across the country in a final dash to sign up uninsured Americans. The HealthCare.gov website, which was receiving 1.5 million visitors a day last week, had recorded about 2 million through noon Monday (local time).
At times, more than 125,000 people were simultaneously using the system, straining it beyond its previously estimated capacity. People not signed up for health insurance by the deadline, either through their jobs or on their own, were subject to a federal tax penalty - a threat that helped drive the rush.
The federal website operating in 36 states stumbled early - out of service for nearly four hours as technicians patched a software bug. An afternoon hiccup temporarily kept new applicants from signing up, and the process slowed further as the day wore on. 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.
The administration announced last week that people who started applying for health insurance but were not able to finish before Monday's enrolment deadline will get extra time.
The law's supporters are already trying to make the next open enrolment season, staring November 15 more consumer friendly.