By Nick Wingfield

New York Times News Service

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.

Randy Hargrove, a Walmart spokesman, declined to comment directly on Amazon but said, “While low prices are at the core of who we are, our customer base cuts across all income levels.”

Over 68 million people were enrolled in Medicaid at the end of last year, a little over half of them adults. (Amazon says the discount applies to adult holders of Medicaid cards.) Many Medicaid participants also receive electronic benefit transfer cards, and Amazon is “very pleased with the response so far” to the discounted Prime membership for those cardholders, a company spokeswoman, Julie Law, said.

Amazon has been so successful at attracting upper-income consumers that it increasingly needs to go elsewhere in search of growth, analysts said. Its Prime program has been a hit in many households, making shopping on the site a far more practical substitute for going to stores. Prime members can typically have goods delivered free in two days.

Amazon says it does not say how many Prime members it has. But Sucharita Kodali, an analyst at Forrester Research, a market research company, said a recent survey of shoppers by her firm had found that a majority of American households with annual income over $100,000 had Prime accounts.