With no sign of progress in a state budget standoff, Virginia Attorney General Mark R. Herring (D) has hired a constitutional law expert to advise him — the clearest sign yet that the state is barreling toward a government shutdown and uncharted legal territory.

State lawmakers and Gov. Terry McAuliffe (D) have one more month to hash out a budget before July 1, when current spending authorization will expire and state appropriations to schools, parks, health regulators and other agencies could stop flowing.

At issue is whether to expand health coverage for the poor as allowed under President Obama’s Affordable Care Act; McAuliffe and the state Senate support doing so, while the Republican-dominated House of Delegates does not. Supporters forced the standoff by attaching the proposal to the state spending plan, leading resolute lawmakers on both sides of the debate to adjourn their regular session in March with no budget in place.

Also in the spotlight are several constitutional questions, notably whether McAuliffe has the authority to keep certain appropriations flowing after July 1 if no budget deal is reached. Under the constitution, only the legislature has the power to appropriate funds.

The governor has also signaled an interest in expanding Medicaid without General Assembly approval, but that, too, remains an open constitutional question for the same reason. Republicans have hinted that they will sue if McAuliffe tries.

Enter A.E. Dick Howard, a longtime professor of law and public affairs at the University of Virginia, whom Herring has hired and who will be paid $500 an hour by the state to study exactly these questions.

Herring said he would like to see a budget passed before the deadline, but he wants to be ready to go to court if that doesn’t happen.

“He doesn’t have a vote in the legislature, so if his preferred resolution doesn’t come to pass, there will be questions that arise as we get closer to that moment and he wants to make sure he’s as prepared as possible to answer those questions in the best way possible for Virginia,” said Herring spokesman Michael Kelly.

It’s not clear what Herring’s role would be in the standoff beyond providing legal advice to the governor and legislature.

Garren Shipley, a spokesman for the Republican Party of Virginia, said the hire is a waste of money.

“Taxpayers shouldn’t have to pay for the administration to navigate the consequences of its own obstruction,” he said.

Howard, the main author of the modern Virginia constitution when it was redrafted in 1971, declined to comment on his new role. His advice to Herring will be considered confidential.

“In light of the current legislative impasse surrounding approval of the biennial budget and whether to include provisions expanding Medicaid coverage, one can reasonably anticipate litigation to result among two or more of the competing factors,” according to a May 23 letter of engagement signed by the solicitor general.

Howard, a legal expert often quoted in newspapers, including The Washington Post, has previously said that McAuliffe has vast powers under the state constitution to protect essential government functions in the event of a shutdown.

“The constitution is not a suicide pact,” Howard told The Post in April. “No matter what the language of the constitution, it simply does not make sense to read it as saying the governor’s hands are tied, rendering him helpless based on a clear danger to the public safety, health and welfare.”

At the time, Howard compared the governor keeping core services operating to a court issuing a temporary injunction to preserve the status quo until a case is decided.

“I think you could argue the governor has a comparable power to keep things as they are, [to] keep them going until you get a policy decision,” Howard said.

Bob Holsworth, a longtime Richmond political observer, called the hire a smart move for Herring, lending him credibility in the face of a highly charged political face-off.

“I think it makes a lot of sense because Dick Howard is generally seen in some ways as instrumental in writing the constitution under which we’re living. Certainly he is in legal circles one of the most respected constitutional jurists in Virginia, in the country and probably the world,” he said.

McAuliffe has made expanding Medicaid under the Affordable Care Act his top priority, and he came into office upbeat about his ability to sell wary House Republicans on opening the program to 400,000 low-income Virginians.

Herring’s move to hire Howard is unusual, Holsworth said, but the attorney general has been adept as using the “bully pulpit of the office in an extraordinarily proactive way.”

In his first four months in office, Herring has declared the state’s ban on same-sex marriage unconstitutional. Not only did he decline to defend the law in a federal court case, but he also submitted a brief on behalf of the plaintiffs. The case is on appeal with the U.S. Court of Appeals for the 4th Circuit in Richmond.

Herring also declared certain undocumented immigrants who came to the United States as children eligible for in-state college tuition.

Herring’s activism has irritated Republicans. Former governor and attorney general James S. Gilmore III said the budget impasse will present yet another test of whether Herring will uphold the constitution.

“Only the General Assembly can appropriate money for state spending,” Gilmore said in a statement. “Creating a political impasse or not getting the political result from the General Assembly is no excuse for trying to govern unlawfully by decree.”

Even Howard had his doubts about McAuliffe’s authority to expand Medicaid. In another Post article earlier this month, he said: “I don’t know what the legal theory would be, frankly.”

Now it’s up to him to figure that out.