SEATTLE — Amazon has had no problem getting affluent households to buy from its online store. But people with low incomes have been less loyal to the retailer.

Now, Amazon is taking another step to persuade them to spend their money on the site.

Starting Tuesday, the company will offer a discount on its Prime membership program to the millions of recipients of Medicaid, the public health insurance program for low-income Americans. They can receive the benefits of Prime — including free fast shipping and video streaming — for $5.99 a month, less than half the standard monthly fee of $12.99.

The move expands an effort started last year, when Amazon started offering the Prime discount to people with electronic benefit transfer cards, used to distribute aid for food purchases.

The push is a further effort by Amazon to go after shoppers who favor Walmart, which has long been a go-to destination for people on tight budgets. AlixPartner, a financial advisory firm, estimates that Walmart accounts for 18 percent of annual spending through the Supplemental Nutrition Assistance Program, the formal name for food stamps.