Two allies of the administration, both of whom spoke on the condition of anonymity because of the controversy surrounding the rollout, said they approached White House officials this year to raise concerns that the federal exchange was not ready to launch. In both cases, Obama officials assured them there was no cause for alarm.

Robert Laszewski, a health-care consultant with clients in the insurance industry, said insurers were complaining loudly that the site, www.healthcare.gov, was not working smoothly during frequent teleconferences with officials at the Department of Health and Human Services before the exchange’s launch and afterward. “People were pulling out their hair,” he said. …

He pointed out that the exchange was built to accommodate 50,000 to 60,000 visitors at a time — fewer than half as many as the enrollment site for the Medicare drug benefit could handle. The number of older Americans eligible for the drug benefit was far greater than the group of uninsured people who will be allowed to buy insurance through the health exchange, Brailer said, but many elderly patients didn’t have home computers at the time, compared with the near-universal access to the Web that exists across the United States today. For a new program that’s had as much advertising as the Affordable Care Act, building a Web site for just 60,000 people at a time “is weird. The math just doesn’t add up,” he said.