WASHINGTON — The Affordable Care Act’s sixth sign-up season opens Thursday amid stabilizing premiums and more choice for consumers.

Nationally, average premiums are going up only by low, single-digit percentages for 2019. In some states, and for some plans, premiums will decline. Fewer areas will see increases. Insurers also are expanding their participation.

Health care ranks among voters’ top concerns going into next week’s midterm elections.

A year ago, it wasn’t even clear if former President Barack Obama’s signature program would survive repeated efforts by President Donald Trump and Republicans to repeal it.

There have been changes. It might be more difficult finding help in enrolling, after the Trump administration sharply scaled back funding for sign-up counselors known as “navigators.” Even so, independent community groups still guide consumers through the paperwork.

And in a change that takes effect Jan. 1, those who decide to opt out of health insurance won’t be penalized come tax time.

Consumers have until Dec. 15 to sign up through HealthCare.gov.

Mike Hewitt plans to re-enroll. “God bless Obamacare,” said the self-employed remodeling contractor from Austin, Texas.

The first year he signed up under the ACA, Hewitt fell off a roof he was working on, shattering his left heel and tearing an arm muscle. “It allowed me to get good health insurance to fix my body,” said Hewitt, who’s in his 50s. He believes the coverage has been worth the $290 he pays monthly in premiums.

“When you have it, it keeps you proactive on taking care of yourself,” he said.

About 10 million people have private policies through HealthCare.gov and state-run insurance markets, with roughly 9 in 10 getting taxpayer-financed help to pay their premiums. An estimated 12 million more are covered through the ACA’s Medicaid expansion, aimed at low-income adults.

Income-based tax credits to help pay premiums remain available. The HealthCare.gov website and call center will be up and running. Coverage is available even if you don’t qualify for financial help, but many cannot afford to pay full freight, and self-pay customers have left the market in droves.

Democrats have made preserving the ACA’s protections for pre-existing medical conditions a major issue. Trump and Republicans have been hitting hard against Sen. Bernie Sanders’ “Medicare for All” plan, saying Democrats are out to destroy Medicare. Republicans haven’t backed off their vow to repeal “Obamacare.”

After repeal failed last year, the Trump administration and GOP-led Congress continued to chip away, making changes that could lead to fewer people enrolling. If younger, healthier people stay out of the market, it will increase taxpayers’ cost of covering those who remain.

Among the major changes:

Repeal of the unpopular requirement that Americans get health insurance or risk fines, gone as of Jan. 1. Experts agree that will reduce enrollment, but differ by how much.

Greater availability of short-term health plans in most states. The Trump administration is allowing such plans to cover up to 364 days, and renewals up to 36 months. Premiums are much lower than for ACA plans, but pre-existing conditions are excluded and plans don’t have to cover basics including prescription drugs.

Expansion of “association health plans” for small businesses and sole proprietors. These plans, which can be sold across state lines, are broadly similar to employer insurance. But it takes time to set up provider networks, and to gain approval from state regulators.

About 11.8 million people signed up during last year’s open enrollment, only about 3 percent fewer than the final season under Obama.