DEL. S. CHRIS Jones, a Republican who chairs the Appropriations Committee in Virginia’s House of Delegates, is proof positive that ideology has trumped common sense in the state GOP. Presented with evidence that expanding Medicaid under Obamacare would save Virginia $1 billion over the next nine years, Mr. Jones (Suffolk) said he didn’t care, his opposition to expansion was unchangeable — and besides, he had “not had a chance to look at these numbers.”

Translation: No matter what the benefit to his constituents, to taxpayers and to the welfare of the Old Dominion, Mr. Jones will not hear of it. He’s sticking to his guns, no matter what the facts happen to be.

The newest estimate is nonpartisan; it was presented by the state’s top health official, William A. Hazel Jr., who was appointed by former governor Robert F. McDonnell, a Republican, and reappointed by Gov. Terry McAuliffe, a Democrat. Mr. Hazel, who is widely respected in Richmond, made the point that the state began formulating the latest estimate last summer and had intended to complete the task last month before Mr. McDonnell left office.

A $1 billion savings over less than a decade is significant, so it came as an unwelcome surprise to Republicans, who were banking on an earlier state analysis that suggested Virginia might incur a modest cost by expanding Medicaid. The revised numbers have the advantage of drawing on experience and data from states that have signed on to the expansion and are covering formerly uninsured patients.

In particular, the state’s revised analysis indicates that federal Medicaid funding would replace state subsidies for some 95 percent of poor and uninsured patients currently cared for by two big public systems — University of Virginia Health System and Virginia Commonwealth University Health System. Previously, officials had estimated that half those patients would qualify for Medicaid funding; in fact, the number will be far higher.

The state’s new analysis also shows that the longer Virginia waits to expand Medicaid — meaning the longer Republicans block it — the more the potential savings will be eroded. Instead of the $1 billion over nine years that Virginia would save by expanding Medicaid now and triggering federal funding, the state would save just $938 million over the same period if it waits until the beginning of next year. In other words, there is a real cost to the GOP’s obstructionism, and it’s quantifiable.

Whether Virginia opts to expand Medicaid or not, poor and uninsured patients will continue to seek medical care, and many of them will do so at state expense. It is a triumph of ideological purity over budgetary prudence for lawmakers in Richmond to insist on spurning federal funds that would only relieve the burden on taxpayers and, in the process, provide a safety net for up to 400,000 Virginians who lack insurance coverage.

Mr. Jones faces a simple decision: Would he rather help needy Virginians or be lionized by dead-enders in the Republican Party for whom anything associated with Obamacare, its actual merits notwithstanding, is anathema?