A recent sticky Friday found Ms. Barker passing out fliers about open enrollment at a back-to-school fair in East Nashville. To every parent and grandparent who strolled past, she asked, “You have health insurance?” Nearby was her favorite prop: a wheel that passers-by could spin with a dial that landed on terms like “deductible” and “penalty,” which she cheerfully explained to those willing to listen.
For the law’s first four enrollment seasons, the Obama administration spent heavily on advertising, recruited celebrities like Katy Perry and companies like Uber to spread the word and scrutinized data to pinpoint potential customers. But this year, community-based enrollment groups, known as navigators, may be largely on their own.
“This is going to be the heaviest lift we have ever tried to undertake,” said Jessie Menkens, navigator program coordinator for the Alaska Primary Care Association. “We will be shouting out for people to recognize this really is not over — that regardless of what deliberations are happening in Washington, this is still truly the law of the land.“
The approximately 100 navigator groups around the country, which received $63 million in federal grants last year, are not sure the Trump administration will renew those grants, which are supposed to be awarded next month. Matt Slonaker, executive director of the Utah Health Policy Project, said he had had encouraging conversations with officials at the Centers for Medicare and Medicaid Services (known as C.M.S.), but “no one will know for sure until the grants are finalized.”
Mr. Slonaker also said that at a conference that C.M.S. held for navigators in June, employees of the agency said the federal government would not run any ads to promote open enrollment this year. A spokeswoman for the agency would not confirm whether that was true or answer other questions about the administration’s plans.
Other open questions include whether the Trump administration will automatically re-enroll people who did not actively cancel or change their plan, as Mr. Obama’s did, and whether it will increase staffing at call centers that help people sign up, given the compressed enrollment time frame.
Insurance companies had asked for the shorter enrollment period, saying it would allow them to collect a full year’s worth of premiums from Obamacare customers and reduce the number of people who wait until they are sick to sign up. The Obama administration had planned to cut the enrollment period to six weeks starting in 2018, but the Trump administration moved it up to this year.
Leaders of the state-based marketplaces say they feel largely in the dark.
“By this time in prior years, the states would have a really good sense of what the federal government was planning so we could plug the holes or leverage what they were doing,” said Mila Kofman, executive director of the D.C. Health Benefit Exchange Authority. “We just haven’t seen any details.”
It seems clear that Mr. Trump won’t be using his powerful Twitter account to encourage sign-ups. Nor are he and Tom Price, his health and human services secretary, likely to be visiting enrollment sites around the country like Mr. Obama and his health secretaries, Kathleen Sebelius and Sylvia Burwell, did.
Mr. Obama visited Nashville to promote the health law in 2015, going to the home of a breast cancer survivor who had benefited from the law, then taking her in his motorcade to an elementary school, where the two of them talked up the law to a cheering crowd.
Last year, Tennessee became a symbol of the law’s growing problems. Insurers sought some of the steepest premium increases in the country after posting major losses they blamed on their Obamacare customers’ high medical costs. Then BlueCross BlueShield of Tennessee decided to stop offering plans in Nashville, Memphis or Knoxville. Statewide enrollment dipped to 200,401 by February 2017, from 231,705 in March 2016.
The state became something of a poster child for the repeal-and-replace effort this year, when Humana announced it was pulling out of the Obamacare markets nationally. That left 16 Tennessee counties with no insurers for next year, a situation Mr. Trump seized on at a rally here in March. (BlueCross BlueShield has since agreed to offer coverage in those counties.)
The Health and Human Services department has produced a series of videos featuring Americans “burdened by Obamacare,” which Mr. Price has posted on Twitter. In response to a request from Senate Democrats, the Government Accountability Office is investigating the videos as part of a broader look at whether some of the anti-Obamacare actions by H.H.S. have violated restrictions on how federal funds can be spent.
Congressional Democrats said they would be sending a letter to Mr. Price on Friday, demanding detailed information about his plans for marketing and outreach during open enrollment. In the letter, the ranking Democrats on House and Senate committees with jurisdiction over health care said they were concerned the administration was “intent on depressing” sign-ups.
“It’s pretty powerful,” Ms. Barker said of the administration’s frequent attacks on the law, “and that’s what we’re up against.”
Ms. Barker’s salary is paid out of the $1.6 million grant that her nonprofit agency, Family and Children’s Services, receives under the law and shares with three other groups around the state. For now she remains upbeat, especially since Senator Lamar Alexander of Tennessee, the Republican who leads the Senate health committee, recently announced the committee would try to create bipartisan legislation next month to shore up the law.
“I’m thinking yes, that’s great!” Ms. Barker said. “I use that when I talk to people who are concerned — there’s a possibility that things will get better, that premiums will go down and this will all get worked out.”
At the back-to-school fair, she buttonholed an uninsured father who said he was moving to Memphis, telling him he might be eligible for a special enrollment period and pressing a phone number into his hand. He gave her a thumbs-up as he walked away.
As the event wound down, she made plans to stop on her way home at a TJ Maxx that was going out of business. Its employees, she reasoned, might need new insurance soon.
An earlier version of this article misspelled the surname of the executive director of the D.C. Health Benefit Exchange Authority. She is Mila Kofman, not Mila Kaufman.
Getting People to Enroll in Health Plans While Trump Attacks Them