ONCE AGAIN, Gov. Robert F. McDonnell (R) has made the case that Virginia urgently needs a major boost in transportation spending. Once again, he’s correctly made the connection between jobs and economic development, and improvements in the state’s severely underfunded roads, rails and bridges. Once again, he has honestly acknowledged that the modest recent steps he has taken to increase funding, such as accelerating borrowing for major new road projects, are inadequate.

That’s why it’s disappointing that Mr. McDonnell’s latest prescription to address the state’s transportation funding crisis is so half-hearted. Given what the governor himself understands is the daunting magnitude of the problem, it’s hard to avoid the conclusion that he is apprehensive about challenging his party’s conservative stalwarts in Richmond.

To be fair to Mr. McDonnell, the 2012 transportation program he unveiled in Norfolk on Thursday is partial; more is to be announced in the coming weeks as the governor puts forth his two-year budget and the legislature convenes in Richmond for its annual session. Conceivably, he is withholding news of a major funding initiative; we’d certainly like to think so, as would the state’s beleaguered commuters.

Judging from what he’s announced so far, though, Mr. McDonnell’s initiative is, at best, a tentative step in the right direction. In keeping with a campaign promise, he would slightly increase the share of year-end surpluses going to transportation, but there is no assurance that surpluses will materialize. Likewise, he would allocate a small extra portion of state funds to transportation when annual revenue growth exceeds 5 percent, but again, there’s no assurance that the state’s economy will grow at that pace.

The governor’s main initiative is to gradually increase, over the next eight years, the share of the state sales tax earmarked for transportation. We’re not happy that that money would be drawn from general funds, affecting education, public safety and health programs. The upside is that it would yield at least $55 million annually in extra cash for roads right off the bat and an extra $300 million a year by 2020.

Fine. But the harsh truth is that in the best-case scenario it will only stop the current bleeding of construction funds that have been siphoned off by the state’s mounting maintenance needs. Virginia needs more. How much more is a matter of debate, but a middling estimate is something on the order of $1 billion annually in new revenue — now, not eight years from now.

Negotiations are underway in Richmond. Those negotiations are largely among Republicans, who now control both houses of the General Assembly as well as the governor’s office. They are wrestling with how to square their campaign promises of no new taxes with the reality — and Mr. McDonnell’s clear understanding — that much more must be done to prevent further deterioration in the state’s sclerotic road system.

The sensible thing would be to raise the state’s gas tax, which was last increased in 1986 and, in addition to having been badly eroded by inflation, is now among the nation’s lowest. The governor has ruled that out, but he has not ruled out other steps — such as indexing the gas tax to inflation — to prevent further depletion of the state’s main funding source for transportation.

Mr. McDonnell has kept his eye on the ball. But the real test of his governorship, and of Virginia’s long-term economic competitiveness, will be his willingness to fight — even at risk to his political standing — to devise a lasting fix to the problem.