Over the weekend, the Trump administration made good on a proposal it’s hinted at for months: It plans to “heavily” consider immigrants’ legal use of public assistance programs when determining whether or not to grant them green cards, the New York Times reports.

The policy change is significant because it will likely discourage immigrants—regardless of status—from signing up for benefits like the Supplemental Nutrition Assistance Program (SNAP, formerly food stamps) or housing vouchers. People who currently use these programs and hope to obtain green cards in the future may be incentivized to drop out.

The proposed rule, which is subject to a 60-day public review period, expands the parameters that define “public charges”: a class  of people who have been excluded from obtaining legal immigration status for more than a hundred years. The government has a long history of preventing public charges  from becoming permanent residents on the grounds that they are likely to become “primarily dependent” on public support and therefore may pose a burden on taxpayers.

Since 1999, the definition of “public charge” has been pretty narrow: It includes people who receive cash benefits or may require long-term institutional care. The Trump administration is now proposing to expand that definition to consider a much wider variety of public benefits.

The change is likely to impact a significant number of people, though it’s unclear exactly how many immigrants would be directly affected. The Kaiser Family Foundation estimated 20 million children would be impacted based on a leaked draft of the rules; New York City officials estimated the changes could affect one million people in the five boroughs alone.

It’s important to note these estimates may overstate impact: they include benefits like Supplemental Nutrition Program for Women, Infants, and Children (WIC) that were not included in the final rule. Yet even though the proposal is narrower than advocacy groups initially feared, it has already had a chilling effect at enrollment offices across the country. Earlier this month, Politico reported WIC agencies in at least 18 states had seen drops of up to 20 percent in enrollment, a change they largely attributed to the rumored change in immigration policy.

If Politico’s findings are any indication, the real impact of the rules may be much greater than the scope of the programs targeted. Even though the version of the proposal that was ultimately published didn’t include the WIC program at all, the mere rumor that WIC use might impact green card status was enough to drive people away from the program in droves. Immigrants unfamiliar with the U.S. welfare system may avoid public assistance altogether for fear of losing their chance to become permanent legal residents.

Unauthorized immigrants are already ineligible for the vast majority of public benefits. But children who are citizens can participate in programs like SNAP and receive health insurance. Vox reports the published proposal won’t punish parents for having kids who use food stamps, but having a large family may be a negative factor in an application.

The proposed rule change may galvanize voters in both parties ahead of November’s midterm elections, according to the Times. Immigration hardliners see the change as long overdue, while advocates will likely see the rule as an assault on immigrant families. Meanwhile, even if the rule is adopted as written, it may not go unchallenged: New York Governor Andrew Cuomo has already said he would sue the Trump administration if it penalizes people for making use of the safety net.