ST. PAUL — Don’t expect that a flood of uninsured Minnesotans will immediately sign up for health coverage on Tuesday, the day that MNsure.com opens for business.

“We’re going to have a lot of lookers, I don’t think a lot of takers right away,” said April Todd-Malmlov, executive director of Minnesota’s newest state agency, set up to deliver new federal health insurance policies to Minnesotans.

Insurance coverage purchased through Minnesota’s online health insurance exchange won’t kick in until Jan. 1, and those seeking immediate coverage on that date have until Dec. 15 to sign up. But that cushion hasn’t stopped a flurry of activity to make sure MNsure is ready for its customers — from last-minute security training for dozens of government employees and private contractors who will handle private information, to daily briefings for Gov. Mark Dayton, who has much at stake in its success.

“It’s one thing to start a small business in obscurity and, if successful, expand it over time and you learn from your mistakes in ways that are not so visible,” Dayton said. “This is starting a huge enterprise from day one under the glare of the public spotlight with all of these people who are wanting it to fail and casting it in the worst possible way.”

Approved by Congress in 2010, President Barack Obama’s effort to expand health coverage to millions of uninsured Americans has divided Democrats and Republicans like few other issues. Republicans in Washington have continued to fight it, with 42 separate votes in the GOP-controlled House to defund it. And their counterparts in Minnesota have raised concerns about MNsure and its operations.

A few recent missteps haven’t helped. Earlier this month, a MNsure employee breached security by sending an email that included Social Security numbers and other private information belonging to 1,500 Minnesota insurance agents to an agent in Burnsville. Todd-Malmlov has said the breach wasn’t linked to the computer systems that MNsure customers will use. She said those will be as secure as private websites where people enter personal information, like banks.

Still, the agency has been busy providing security training for employees, the private “navigators” who will get financial incentives to help people sign up, and case workers with Minnesota counties who will also help certain groups of people enroll. That training was still in progress at the end of last week; Todd-Malmlov said she had hoped it would be done sooner, but many of the computer systems that require training haven’t been up and running for long enough.

“MNsure is not ready for prime time,” said state Rep. Peggy Scott, a Republican from Andover. Critics also keyed on the slow distribution of grants to groups that will help enroll people in MNsure, which were still in the works even at the end of last week. Scott and other Republicans have sought a delay in MNsure’s launch.

Within a few years, the state forecasts that about one in five Minnesotans, or about 1.3 million people, will buy their insurance through MNsure, including about 300,000 people who don’t have insurance now. Senior citizens covered by Medicare will continue to get their insurance that way. Most people who get insurance through their employer will continue to do so, though businesses with fewer than 50 employees will be eligible to insure them through MNsure.

Under the federal law, people who don’t have health insurance will face a tax penalty starting a few months into next year. People with lower incomes will be eligible for tax subsidies to help cover their costs, and studies have shown that most new enrollees won’t end up paying any premiums. Those participants will still be responsible for co-pays and other out-of-pocket costs.

Under the rate structure, a family of four with an annual household income below $31,300 would likely qualify for free health insurance. Free coverage would also extend to people earning between $15,000 and $17,000.

MNsure will have some plans with monthly premiums as low as $91. Rates are based on a variety of personal circumstances, including age, location in the state — southeastern Minnesota is forecast to have higher rates than elsewhere — family size and tobacco use. Supporters hope the federal law brings down health costs overall, but they have acknowledged it’s likely to mean higher premiums for some participants.

MNsure’s leaders don’t expect heavy enrollment in the first few weeks, but they plan to closely track customer interactions with both their website and call center. Todd-Malmlov said tracking both levels of participation as well as customer concerns from different parts of Minnesota will guide future outreach and marketing efforts. “We do certainly think there will be a lot of traffic immediately, because people are curious,” she said.

Members of MNsure’s board of directors have downplayed expectations for initial enrollment, some even advising prospective customers to wait a bit before signing up. Board member Thompson Aderinkomi said as with any new technology, people might want to wait for kinks to be worked out. “There’s nothing wrong, actually, in asking people not to sign up right away,” he said.