SANTA FE, N.M. (AP) — New Mexico stands to lose critical funding for substance abuse treatment that has helped combat a local opioid epidemic, under a Republican campaign on Capitol Hill to roll back President Barack Obama's health care law.

A House-approved health care bill would phase out expanded Medicaid that allows states to provide federally backed insurance to low-income adults. Federal Medicaid expansion dollars have allowed key states to boost their response to the opioid crisis, paying for medication, counseling, therapy and other services.

In New Mexico, the expansion accounted for...