By Michael D. Shear

New York Times News Service

HOLLYWOOD, Fla. — The hunt for the uninsured got underway one recent afternoon when 41 canvassers, armed with electronic maps on Samsung tablets, set off through working-class neighborhoods to peddle the Affordable Care Act door to door. Four hours later, they had made contact with 2,623 residents and signed up exactly 25 people.

Many of their targets, people identified on sophisticated computer lists generated in Washington as unlikely to have health insurance, had moved away. Some were not home. Many said they already had insurance through Medicare, their parents or a job. A few were hostile at the mere mention of President Barack Obama’s health care law.

“We’re going to repeal that,” one man said gruffly as he shut the door in the face of a canvasser, Nancy Morwin, 58, a retired social worker.

Such are the limits of microtargeting the uninsured as groups supporting the Obama administration take to the streets on behalf of the president’s most important domestic initiative. The nationwide effort is modeled on Obama’s voter turnout machines in 2008 and 2012, but in this case the task of finding Americans without health insurance and signing them up is a slow grind.

Although the administration expects many enrollees to make their own way to the government’s health care website or the state exchanges, the door-to-door effort is aimed at people without computers, email addresses or the wherewithal to show up at health fairs and other enrollment events.

The campaign is staffed by organizations deploying thousands of paid and volunteer canvassers across the country. Now, with finally working, Obama administration and outside supporters are racing to meet their goal of signing up 7 million people by March 31. By the end of January, nearly 3.3 million people had enrolled. To the canvassers, at least, the original goal seems a long way off.

Nicholas Duran, Enroll America’s Florida director, said his group plans to be even more aggressive before the March 31 deadline. “The intensity is definitely ramping up,” he said, comparing the efforts to reach the uninsured to candidates’ efforts to reach voters. “They are going to hear from us multiple times between now and the end of March.”

The canvassers’ lists are derived from data created at Enroll America, a nonprofit group that is trying to expand the health care rolls, by some of the same computer programmers who churned out statistical models for Obama’s presidential campaigns. Using commercially available information, the data experts generate lists of people with rankings that indicate their likelihood of needing health insurance. The typical uninsured is younger, male and either low-income or unemployed.

In some cases, problems with the health care website are still frustrating the canvassers’ best efforts. Ryanbo Morales, 27, a Planned Parenthood worker, found Chrystal Rhodes, 24, who said she did not work enough hours at JetBlue to qualify for its insurance. But his efforts to help her sign up on his Samsung tablet were stymied when she kept getting an enrollment error. “This is really unfortunate,” Morales said.