Lawmakers who have voted against expanding Medicaid to about 70,000 low-income Maine residents have leaned heavily on the defense that affordable health coverage is already available to a majority of those who would qualify for an expanded Medicaid program — courtesy of the Affordable Care Act’s online health insurance marketplace.

Those staunchly opposed to expanding Medicaid have handed out fliers and encouraged low-income Maine residents to log onto the Affordable Care Act’s and enroll in subsidized private insurance plans. They’ve characterized the push for Medicaid expansion as an attempt to enroll Maine residents in state welfare programs.

Residents whose incomes fall below the federal poverty level ($11,670 for a single person) have even been encouraged to claim a higher estimated income — a “goal of improving your own economic future” — in order to qualify for federal health insurance subsidies. Under the Affordable Care Act, subsidies kick in for those earning 100-400 percent of the federal poverty level.

Now, the deadline to enroll in insurance through has passed. Lawmakers are awaiting Gov. Paul LePage’s certain veto of a Medicaid expansion proposal put together by moderate Republicans designed to address Republican concerns about Medicaid expansion.

The Republicans who remained opposed to that expansion proposal might have had a convenient argument against expanding Medicaid in encouraging low-income residents to seek coverage through But they weren’t pushing a true coverage alternative.

That’s not only because the push for subsidized insurance leaves out more than 25,000 of Maine’s poorest residents who have no affordable coverage option. It’s also because health insurance premiums and other cost-sharing requirements, however small, often have the effect of deterring those with limited income from signing up for coverage and using preventive health care.

In the 1970s and 1980s, the RAND Health Insurance Experiment set out to determine the effect of cost-sharing requirements for medical care on the amount of health care patients used and their overall health. For most of the population, cost-sharing requirements had the effect of lowering costs without significantly affecting patient health. Those with low incomes, however, experienced adverse effects from the switch to cost-sharing — particularly when it came to managing chronic diseases.

“More generally, research shows that patients are not good at distinguishing between care that is necessary and care that is not, with the result that cost sharing leads to reduced use of preventive services and essential drugs,” Drs. Brendan Saloner, Lindsay Sabik and Benjamin Sommers wrote March 27 in an article on the New England Journal of Medicine website.

Ultimately, chronic diseases that go undiagnosed and untreated fester into more significant health problems that require emergency room visits and hospital stays when consistent, preventive care all along could have kept those conditions under control at a lower cost.

Other research has pointed to the powerful effect even nominal premiums have in deterring enrollment in health coverage.

In 2003, Oregon’s Medicaid program started charging low-income childless adult enrollees — part of the population that would gain coverage through Medicaid expansion — monthly premiums of $6-$20 along with increased copayments for care. In fewer than three years, enrollment among those charged premiums dropped 77 percent, showing the power of even nominal premiums among low-income populations.

Those who remained enrolled and were charged premiums and increased copayments experienced worse health outcomes than those in Oregon’s Medicaid program who weren’t charged premiums.

Through Medicaid expansion, Maine has the chance to deliver affordable health coverage to some of its poorest, uninsured residents at limited cost to patients and to the state. It’s the best option to ensure Maine’s low-income residents gain crucial access to regular, preventive health care.

The “alternatives” opponents point to won’t enroll all the low-income residents who need coverage and, through premiums and steeper cost-sharing charges, are more likely to leave those with low incomes without care they need.