(Credit: Centers for Medicare and Medicaid Services)

Managers of most of America's public, web-based supermarkets for health insurance are letting consumers sign up for individual and family major medical coverage after the widely publicized Dec. 15 deadline.

The drafters of the Affordable Care Act created the ACA public exchange system to give consumers an easy way to shop for health coverage from ordinary commercial health insurers, and to distribute ACA premium tax credit subsidies.

The team that runs the biggest ACA public exchange program — HealthCare.gov — announced earlier this year that the "open enrollment period" for 2020 coverage, or time when consumers can sign up for individual and family coverage without showing that they have what the government classifies as a good reason to be shopping for coverage, would run from Nov. 1 through Dec. 15.

But the Centers for Medicare and Medicaid Services (CMS), the agency in charge of HealthCare.gov , announced today that, because of heavy traffic and signup system problems that occurred Sunday, it will push the deadline for signing up for 2020 coverage to 3 a.m. Eastern Time Wednesday.

Consumers who want to get covered through HealthCare.gov for 2020 can return to the website to sign up for coverage, CMS officials said in the deadline extension announcement.

If consumers left their contact information with the HealthCare.gov call center and were already in line to get covered, they "do not need to come back and apply during this extension, because a call center representative will follow up with them later this week," officials said.

Earlier today, the HealthCare.gov website was still saying that the open enrollment period ended Dec. 15. Around 3 p.m. Eastern Time, managers added a note saying that the deadline has been extended.

HealthCare.gov provides ACA exchange signup and account administration services for many states. Other states run their own exchange programs.

Open enrollment period basics

Health insurers, regulators and ACA exchange program managers developed the open enrollment period to cope with the fact that the ACA eliminated many of health insurers' defenses against the problem that sick people are more likely to pay for coverage than healthy people are.

An "open enrollment period," or limits on when it's easy for people  to buy coverage, is supposed to push healthy people to pay for coverage, by scaring them with the thought that, if they try to wait till they get sick to get covered, they may find themselves with huge medical bills and no way to buy health insurance.

Health insurance market policymakers may find extending open enrollment period deadlines a simple way to increase the open enrollment period's marketing power. The extensions tend to get plenty of free publicity; give consumers more time to sign up for, and pay for, coverage; and increase consumers' awareness of the idea that missing the enrollment deadline is bad.

Beyond HealthCare.Gov

Here's how the state-run ACA exchange programs appear to be handling their enrollment deadlines, based on information on the exchange websites and the exchange programs' Twitter feeds.

California (Covered California): Covered California started with an open enrollment period running from Oct. 15 through Jan. 31. On Friday, it pushed the deadline for coverage starting Jan. 1 to Dec. 20, from Dec. 15.

Colorado (Connect for Health Colorado): Connect for Health Colorado has an open enrollment period set to run from Nov. 1 through Jan. 15. The exchange inched the deadline for coverage that starts Jan. 1 back to 6 p.m. Mountain Time today, from Dec. 15.

Connecticut (Access Health CT): Access Health CT started with an open enrollment period that ran from Nov. 1 through Dec. 15. Today, the exchange pushed its enrollment deadline for 2020 coverage back to Jan. 15.

District of Columbia (DC Health Link): DC Health Link has an open enrollment period that started Nov. 1 and is set to run until Jan. 31. Members of Congress and some of their aides who want employer-sponsored health coverage are supposed to get it through DC Health Link. Rep. Alexandria Ocasio-Cortez, D-N.Y., drew attention to DC Health Link Sunday by tweeting that, on her exchange, she has a choice of 66 different plans to wade through, and that the process is too confusing.

Idaho (Your Health Idaho): Your Health Idaho started with an open enrollment period that ran from Nov. 1 through midnight today. At press time, it appeared to be sticking with the midnight today deadline.

Maryland (Maryland Health Connection): Maryland Health Connection set its open enrollment period to run from Nov. 1 through Dec. 15. At press time, the exchange appeared to be holding firm on the Dec. 15 enrollment deadline.

Massachusetts (Massachusetts Health Connector): The Massachusetts Health Connector has an open enrollment period that's set to run from Nov. 1 through Jan. 23.

Minnesota (MNsure): MNsure has an open enrollment period that's set to run from Nov. 1 through Dec. 23.

Nevada (Nevada Health Link): Nevada has taken back control of its exchange from the HealthCare.gov team. It was going to have its open enrollment period run from Nov. 1 through Dec. 15, but it announced today that it will give people who have already started an application until Dec. 20 to finish enrolling.

New York (New York State of Health): New York State of Health has an open enrollment period that runs from Nov. 1 through Jan. 31.

Rhode Island (HealthSource RI): The HealthSource RI open enrollment period runs from Dec. 1 through Dec. 31.

Vermont (Vermont Health Connect): Vermont's open enrollment period was set to run from Nov. 1 through Dec. 15. At press time, it appeared it to be holding firm on the Dec. 15 deadline.

Washington State (Washington Healthplanfinder): Washington Healthplanfinder set its open enrollment period to run from Nov. 1 through Dec. 15. The exchange is now saying that it will give people until Dec. 30 to sign up for coverage that starts Feb. 1.