NOT FOR THE first time, Virginia Gov. Robert F. McDonnell (R) has delivered a blunt assessment that the state is fast running out of money to build and improve its roads, bridges and rails. Once again, he has promised to seek new funds before the demand for upkeep drains away the last precious dollars for new construction.

But even as the governor delivers a spot-on diagnosis, his prescription — which includes the proviso that any funding change be revenue-neutral — ensures that Virginia’s sickly transportation network will continue to waste away.

At the start of this year, Mr. McDonnell toyed with a transportation idea that has long intrigued him: indexing the state’s fuel tax for inflation. The fuel tax is Virginia’s main source of transportation revenue, but it hasn’t been raised since 1986. Since then, inflation and better auto fuel efficiency have decimated its buying power. Mr. McDonnell’s idea wouldn’t solve the problem, but it would at least stop the bleeding.

The governor has long acknowledged this, though rarely in public for fear of provoking his fellow Republicans in Richmond. As it turned out this year, his fears were well-founded. When he broached the idea of indexing the gasoline tax in January, GOP lawmakers blanched and Mr. McDonnell backed down. The result: another wasted year as the Zero Hour — zero new dollars for transportation construction — approaches.

It’s not surprising that Virginia Republican lawmakers are wary of tax indexing, which they demagogically equate with a tax increase. What is surprising is the lack of fight in Mr. McDonnell, who is genuinely alarmed at the bleak outlook for the state’s infrastructure funding. He knows that maintenance is consuming all highway revenue — “This is not a political statement; it’s simply math,” he told the Associated Press — but he won’t raise taxes to tackle the problem.

Indexing the gas tax to inflation, along with a modest transfer of funds to roads and rails from education, public safety and social services (which most Democrats and some Republicans oppose), would restore about $1 billion a year for transportation within five or six years.

Mr. McDonnell told the AP that indexing is worth considering — the same wan formulation he has used for years. But his aides hastened to say that indexing might be considered a tax increase, so offsetting tax cuts would be needed. In fact, indexing would simply prevent the state’s revenue from shriveling to nothing.

Gubernatorial leadership is the only way out of the state’s transportation funding mess. In this case, that means Mr. McDonnell must challenge the Republican caucus and make his case for indexing publicly, by puncturing the myth that it is a tax increase. A sotto voce campaign has been inadequate to the task, and the result is a crisis that the governor fully grasps but has done nothing to solve.