For the working poor, layoffs and other household changes can result in big financial setbacks, making it impossible for them to pay even modest monthly premiums. That’s why the health reform law always envisioned having expanded Medicaid coverage to help pick up the tab.

But many Republican-dominated states have refused to expand their Medicaid programs, which would cost them little or nothing through 2016 and not that much more in subsequent years. Under the A.C.A. as interpreted by the Supreme Court, states have the option of expanding Medicaid to provide largely free health care to people earning up to 138 percent of the federal poverty line, or about $33,000 for a family of four, with the federal government paying most of the cost. However, in 20 states that have not expanded Medicaid, poor people are forced to rely on federal subsidies to help them buy private insurance; those subsidies leave many of them exposed to premiums they can’t afford when they lose their jobs or have very little income.

One vexing problem is that many people are confused by the various notices telling them what information they need to submit to obtain subsidies. Some 423,000 people in 37 states that use the federal marketplace lost their 2015 coverage because they failed to document their citizenship or immigration status, and 967,000 households had their subsidies recalculated because of discrepancies in their original reports of household income. Often, problems arose because people failed to submit their Social Security numbers.

The Obama administration has been simplifying its messages to make enrollment easier. States that have not expanded Medicaid should do so to help their own low-income citizens, but the Republicans in those states would rather have their residents suffer. Stronger outreach efforts by enrollment counselors might also help people understand what documentation they need to provide.

The penalty for failing to obtain insurance will rise steadily in coming years, which could spur more enrollment. The penalties can’t be calculated precisely until a person files income tax returns. But if people were given more information about the penalties at the start of the enrollment season on Nov. 1, those who can afford to pay premiums might have even greater incentive to enroll.