Washington • With just over a week now left in the sign-up period for 2019 Obamacare plans, new figures show enrollment is down compared with last year. Overall, sign-ups through HealthCare.gov, the federal Affordable Care Act exchange, are down 11 percent through the first five weeks compared with the same time last year -- and experts say final numbers are on track to be lower overall at the end of enrollment.

It's still possible for a surge in the final days, as people wait until the last minute to choose health-care plans for 2019.

But experts who have been following ACA enrollment closely say several factors may have contributed to an overall drop, including some of the Trump administration's policies that Democrats have warned could have a negative impact on insurance marketplaces. A combination of those efforts, including a drop in federal spending on advertising and outreach, the repeal of the individual mandate, and the move to open the door to alternative health plans, as well as factors such as less media coverage surrounding enrollment and lower unemployment rates, could all be blamed.

The Centers for Medicare and Medicaid Services announced Thursday that from Nov. 1 to Dec. 1., a total of 3,198,163 people had selected ACA exchange plans. That's down from 3,604,440 at the fifth week of enrollment last year.

Josh Peck, who served as Healthcare.gov's chief marketing officer under the Obama administration and is now a co-founder of Get America Covered, published an analysis predicting total enrollment on the federal exchange would fall by 800,000.

There are also fewer people enrolling for the first-time in the marketplaces.

Cynthia Cox said new consumers were down about 18 percent compared with last year, and the number of people visiting Healthcare.gov down almost 21 percent.

"You look for explanations, is it that people aren't coming to the site? Is it that maybe they don't know about it? Is it the repeal of the individual mandate? Is it that they just don't want insurance?" Cox, director of the study of health reform and private insurance at the Kaiser Family Foundation, told me in an interview. "That's one clue as to what the driver is: Are people even coming to the site or not? And there's an even bigger drop in the number of people visiting the site and of new consumers than there is a drop of people who are signing up at all."

Cox said the elimination of the tax penalty for people who did not sign up for health coverage, which was repealed as part of the GOP tax overhaul last year, may have had an impact on the decline. She also said with lower unemployment rates, consumers may be moving to employer-sponsored plans.

But lack of awareness of ACA enrollment may be one of the biggest factors contributing to the decline, Cox suggested. "The latest #ACA numbers suggest the drop in signups is primarily due to lack of awareness & possibly mandate repeal, more than lack of appealing plans," she wrote on Twitter.

That awareness gap could be a result of the Trump administration's decision to dial back Obamacare advertising and to dramatically cut funding for groups, known as navigators, meant to help people obtain health insurance under the ACA.

But Joseph Antos, a health-care scholar at the conservative American Enterprise Institute, said it's not enough to point fingers at the administration.

He said there was also a drop in news coverage of ACA enrollment over the past year, in part due to the intense coverage of the midterm elections that "crowded out talk of health insurance."

"I'm arguing it doesn't matter who pays for the ads, where the news comes from," Antos told me. "What matters is how much of it was focused on health insurance vs. everything else."

But he said that could change going forward. "If we look again this time next year, what will we see?" he asked, arguing that as Democrats retake control of the House, "there will be a lot more talk about health insurance and a lot more reporting on it."

Antos also suggested navigator grants, although helpful for some individuals, may not have markedly helped with enrollment overall in past years.

Larry Levitt, senior vice president for health reform at KFF, points to other factors that could be contributing to the decline, including access to leaner, cheaper plans the Trump administration made available this year.

Some experts told me it's too soon to tell whether those alternative plans have had a major impact on enrollment. Health 202 author Paige Winfield Cunningham wrote at the beginning of the enrollment season that such plans test GOP "actions to put a more conservative stamp on the ACA."

The lag is not just happening at the federal marketplace level. Although several states that run their own exchanges have seen an increase in enrollment thus far, some are seeing a slight drop, too.

In New Jersey, the only state that implemented its own individual mandate after it was repealed at the federal level, enrollment in the federal marketplace has still lagged compared with last year.

Democratic Gov. Phil Murphy and his administration made a big marketing push to urge residents to enroll. Still, enrollment as of the fifth week was down more than 13 percent compared with last year.

Raymond Castro, director of health policy at progressive think tank New Jersey Policy Perspective, said part of the problem may be that people aren't aware of of the state's mandate. "Most people are reading that the national individual mandate is now gone, and they aren't getting our news that we still have it in New Jersey." He said those consumers will realize the change once they are forced to pay a penalty.

But Castro said he was optimistic about a surge in sign-ups in the final days of enrollment, as well as for future enrollment periods. "I think there will be some turnaround," he said. "With the combination of the individual mandate and lower premiums, I don't see why we shouldn't."

In California, one of the dozen state-based marketplaces, there has also been a major marketing push, but enrollment is also down slightly. Covered California noted while the number of new consumers has dropped about 11 percent to 90,500 compared with the same time last year, it's ahead of where sign-ups were in 2016.

"On the whole we feel pretty good about the enrollment numbers. We always projected there will be a drop in enrollment because of the [individual mandate] going away," Peter Lee, executive director of Covered California, told me. He also pointed to a delay in marketing until after the November election. But he stressed that for the state's exchange, which allows enrollment through Jan. 15, it's still very early.

"The next two weeks matter, and matter a lot," he added. "I think there's cause for very significant concern at the pulling back on federal marketing dollars . . . There's no doubt that if you cut back on marketing dollars, enrollment is going to decline."

In Colorado, where the state exchange, Connect for Health Colorado, controls its own marketing and outreach, enrollment is so far up nearly six percent compared to the same point last year.

Luke Clarke, a spokesman for the exchange, said it's still too early to determine if sign-ups will be up overall after enrollment in the state ends on Jan. 15. But he pointed to lower premiums, and improvements to outreach efforts, as some of the reasons for the spike.

“We control our own fate. We haven’t cut our marketing; we haven’t increased it, either, but we’ve kept it steady,” Clarke said, adding the state would continue its marketing efforts because “it’s working.”