VIRGINIA GOV. Robert F. McDonnell (R), under attack by his erstwhile conservative allies for having overseen the enactment of a desperately needed tax increase for transportation, is trying to protect his right flank by vowing not to permit any expansion of Medicaid while he is governor. We salute Mr. McDonnell for his guts on the transportation bill, but on Medicaid he is posturing. Even under the most aggressive scenario, the state would not be in a position to expand Medicaid before July 2014 — six months after Mr. McDonnell leaves office.

Still, that sluggish pace raises a broader question: Why is Virginia, one of the seven or eight richest states, one of the stingiest in providing health-care coverage for its poorest residents, including the working poor? It currently ranks 48th in per capita spending on Medicaid. Has the state’s flinty tightfistedness become callous indifference?

Under the Affordable Care Act (Obamacare), states have the option of broadening eligibility for Medicaid — the main federal health insurance program for the poor, elderly, blind and disabled. If Virginia exercised that option, at least 400,000 of the state’s 1 million uninsured people would become eligible for coverage.

For the first three years, the feds would foot 100 percent of the bill for these newly insured people, with the federal share declining to 90 percent in 2020. That’s a much better deal than the 50-50 split between the federal government and the states in force for current Medicaid recipients.

But Mr. McDonnell balked, as did most Virginia Republicans, complaining about Medicaid’s inefficiencies. He did so even as Republican governors elsewhere, suddenly struck by the notion that poor people need and deserve health coverage, shed their previous opposition and said yes to the federal dollars — in most cases with a green light from Washington allowing them to pursue reforms.

Under pressure from Democrats in the state Senate, who threatened to torpedo the transportation bill unless Mr. McDonnell relaxed his opposition to Medicaid expansion, he gave ground — sort of. He allowed the creation of a 10-member commission of lawmakers that will certify whether Medicaid has been sufficiently reformed to justify its expansion in Virginia. Now he is being attacked by tea party types who say he has abandoned conservative principles.

What exactly are those conservative principles? That Richmond should block federally subsidized health coverage for Virginians unless they are practically starving? (Under the state’s rules, a family of four could earn no more than about $7,000 annually to qualify for Medicaid.) Or that patients lacking coverage should continue to burden hospitals by seeking unreimbursed care, forcing health-care providers to transfer the cost to insured patients, who will have to pay higher premiums?

Republican governors in Arizona, Florida, Michigan, Ohio and elsewhere have realized that continuing to obstruct Medicaid expansion is self-defeating, as well as gratuitously hostile to the needy. In addition, expansion makes good macroeconomic sense; in Virginia, it would mean an infusion of an estimated $20 billion in federal funds over 10 years, money that would provide jobs in the health-care industry and the overall economy. What is Richmond waiting for?