Senate Republicans set on reworking the Affordable Care Act are considering taxing employer-sponsored health insurance plans, a move that would meet stiff resistance from companies and potentially raise taxes on millions of people who get coverage on the job.

The move could raise billions in revenue that could be used to help stabilize the fragile individual insurance market. But it could be politically risky, since it could expand the impact of GOP health proposals from Medicaid recipients and those who buy insurance on their own to the roughly 177 million people who get coverage through their employers.