Her clipboard said the man who lived in the pink stucco apartment building a few blocks from the hotel-lined beach might not have health insurance. So Laura Botero climbed the darkened staircase to the second floor and knocked on the door.

Eduardo Devine, 49, an unemployed beach waiter in black, square-framed glasses, peeked into the dim hallway. He confirmed he had been without coverage since he was laid off a month ago, and his face lit up when Botero mentioned “Obamacare.”

“I just heard about it on the news, but I don’t know how it works,” he said, taking a pamphlet. “It will help. That’s all I know.”

It was a small but critical victory for Botero, a volunteer for Enroll America, a nonprofit group that is fielding a small army to spread the word about Obamacare. In recent weeks, President Obama’s signature health-care law entered a new phase as hundreds of advocates began the arduous task of identifying the uninsured and coaxing them, one by one, to sign up for coverage.

For the law to succeed, groups such as Enroll America, whose officials include several veterans of Obama campaigns, will need to cajole millions of Americans, including many healthy ones, to enter the insurance market. It could be a tough sell. Confusion about the law is rampant. The online insurance sites, which open for enrollment Oct. 1, could be tricky. Some people who rarely need medical care might view even low-cost health plans as too pricey.

See how the states have sided on some of the key provisions of the Affordable Care Act.;

And while advocates say that knocking on doors is one way to overcome these challenges, skeptics point out that such canvassing, which is modeled on successful political campaigns, is untested for a complex national program such as the Affordable Care Act. It’s also labor-intensive; Botero’s group, Enroll America, expects to talk to each person seven to eight times to encourage enrollment in a health plan.

“Obviously, we’ve got to find the uninsured, but we’ve got plenty of examples of finding the uninsured and letting them slip away,” said Stan Dorn, a senior fellow at the Urban Institute and a supporter of the law. He said such campaigns work only if the volunteers take the extra step of filling out the people’s forms — an even more laborious role that Enroll America does not plan to undertake.

Enroll America and other groups, including insurance companies and state health departments, are nevertheless taking their pitches directly to people’s doorsteps.

High stakes

Starting next year, virtually all Americans must carry health insurance or face a fine. But advocates do not expect the penalty, which will start at $95 for the first year and rise to $695 or more annually for an individual in 2016, to be enough of a motivation. That is why they are relying on Enroll America and other groups to make the hard sell to people who, for various reasons, may not be eager to enroll.

A particular challenge is that 2.7 million of the new enrollees must be cheap-to-insure young and healthy people; otherwise, there will be too many older, sicker people and costs and premiums will rise.

In Florida, Enroll America’s work carries particularly high stakes because as much as 25 percent of the non-elderly population lacks insurance and Republican leaders have refused to implement the law’s key provisions themselves. White House officials, who aim to sign up 7 million people nationwide for coverage by next year, have said the state is among their top targets because it has the nation’s third-largest uninsured population after California and Texas.

Over the weekend, more than 100 volunteers with Enroll America knocked on about 4,000 doors around the state.

Among the volunteers was Botero, who carried a list of names and addresses generated by a “microtargeting” tool developed by Enroll America. It is the biggest nonprofit working on Obamacare enrollment, and its work is funded by large philanthropies, insurers, pharmaceutical companies and others invested in the success of the law.

The organization, using census data, commercially available consumer databases and demographic information such as age, race and income, developed a formula to determine the likelihood that someone is uninsured.

The group’s officials say their system works. So far, about 1 in 3 of the people they have reached through their door-knocking efforts, which began in June, are uninsured, they said.

Group officials argue that the door-to-door strategy also makes sense because of the basic geography of the uninsured: Many are clustered in dense neighborhoods, making them easy for a canvasser to reach on foot.

About half of the nation’s uninsured people are concentrated in just 3.8 percent of counties, according to an Enroll America analysis of Census Bureau data. Nearly 5 percent of the nation’s uninsured are in Los Angeles County alone. Miami-Dade County, which includes Miami Beach, is the U.S. county with the fourth-largest uninsured population.

Group officials say they have gotten a generally warm reception at the doors, where they find people have heard about the health-care law but are hungry for information.

“They don’t get their backs up,” said Ray Paultre, the group’s Florida organizing director and a former Obama campaign staffer. “They are sensitive and skeptical because they are talking about their lives and because health care is the most intimate thing you can talk to a person about. But the response has been more thankful.”

Hitting the streets

Botero was among about a dozen unpaid volunteers who turned up on a recent Saturday morning at her business, a nutritional supplement shop, to get quick training and to help Enroll America with its canvassing efforts that day.

Botero, 33, said she is passionate about good health. A Colombia native whose mother-in-law pays for her health insurance, she said she is stunned that so many Americans lack coverage.

“Oh my God, it is crazy here that they don’t have insurance, even if they are working,” she said.

So she set off in a fanny pack and jeans to find some uninsured people in the palm-shaded art deco apartment complexes that are within view of the beach. They contain a mixture of beach bums, retirees, Cuban Americans and immigrants from the Caribbean. Many of the residents are poor or working class.

The first few doors yielded no response. But Botero was itching for a conversation, so she decided to call out to a shirtless young man sitting on the staircase whose back was inscribed with tattoos.

Mikell Cogshell, 25, glanced skeptically at her when she raised the issue of health insurance but warmed to the conversation within a few minutes. “I’m a boxer,” he said, “and I get insured for every fight, but I don't have anything the rest of the time. I know something could happen.”

A question that came up repeatedly as she approached people was: How much will insurance cost?

Botero didn’t have an answer, because the cost depends on the person. But that wasn’t her job anyway. Her goal is to steer people to the government Web site or phone line, where trained guides can walk them through their options based on their income and other factors.

Botero moved on to a pastel pink and green apartment building that was supposed to house 11 of the names on her list. But the building appeared deserted, with trash strewn in the yard. A security guard stepped out of the back door to ask what she was up to, but his face softened when she explained why she was there.

“Oh, that’s Obamacare?” Jean Louis Chrisn said, studying the pamphlet Botero handed him. The 35-year-old native of Haiti, who has been in this country for five years, said he has never had insurance because he never knew how to go about it. “I know you are supposed to have insurance in your life.”

Botero noted his name and address. The information will be entered into Enroll America’s database, which means Botero or another Enroll America volunteer will be knocking on his door one day soon.