With a possible federal government shutdown just hours away on a tense afternoon last month, Sen. Mark R. Warner sounded frustrated.

“As a business guy and someone who’s done this as governor,” the Virginia Democrat told reporters on a conference call April 8, he could not understand why the White House and congressional Republicans had not agreed on a budget.

“I wish I was in the room,” he said.

Now, with a government shutdown averted and the prospect of a broader budget-cutting agreement on the horizon, he is in the room. At times, the room has been Warner’s own office — even the kitchen of his Alexandria home.

Along with Sen. Saxby Chambliss (R-Ga.), Warner is the co-leader of a bipartisan band of senators — a rare blend of liberals, moderates and conservatives dubbed the Gang of Six — that has been working for several months to write legislation inspired by the recommendations of President Obama’s fiscal commission.

As early as this week, Warner’s group could unveil the most comprehensive deficit-cutting plan offered in the current debate — a combination of spending cuts and changes to the tax code and entitlement programs that could ignite controversy but also boost hopes for a budget deal.

“We are closing in on it,” Senate Majority Whip Richard J. Durbin (D-Ill.), a member of the Gang of Six, said last week. “There are still several items left to resolve, but I can see the finish line.”

Warner sounded a more cautious note.

“There are days I’m confident. There are days I’m not confident,” he said.

But Warner can take comfort from having been through this before — in Richmond.

As Virginia governor seven years ago, Warner persuaded a GOP-led legislature to adopt a budget that made record new investments in education, public safety and health care by imposing higher sales and cigarette taxes.

“Certainly, 2004 was a situation where the betting was against us and the conventional wisdom was against us, similar to the way this process has evolved,” Warner said.

This time, the final agreement will be skewed more toward budget cuts. Warner has suggested the breakdown would be $3 in spending reductions for every dollar in increased tax revenue, similar to the ratio proposed by the fiscal commission last year and by Obama in mid-April. The proposal — which includes reducing the national debt by $4 trillion — could alter some cherished tax deductions for mortgage interest and charitable donations while cutting spending for defense and in other previously sacrosanct areas.

The Virginia Republican Party has tried repeatedly to use the 2004 fight to brand Warner as a liberal tax-lover, a message they are sure to reassert if the Gang of Six compromise includes any proposal to raise taxes.

At the same time, the current negotiations have sparked worries among some Democratic leaders about what the group will propose, particularly when it comes to Medicare and Social Security.

“There’s a lot of anxiety out there, I think, on both sides, about what we might ultimately agree to,” Chambliss said. “At the end of the day, everybody’s going to have to swallow something, just like we’re asking the American people to do.”

The dynamic in Richmond was similar, Warner said, but he added: “I think it’s harder at the national level. There’s more pressure.”

Deliberate, personal

The 2004 deal was one Warner personally negotiated over hours of late-night phone calls with Republican state lawmakers, dinners at Richmond restaurants, drinks at the governor’s Executive Mansion and pickup games on basketball courts.

“It was very personal, very intense and very dogged, in a round-the-clock kind of way,” said Preston Bryant, a former state delegate who helped lead a coalition of 17 Republicans who abandoned their conservative leadership in the state’s GOP-held House and backed Warner’s plan.

It was also very deliberate. Warner and his team started the process by compiling a binder that included every statement on taxes ever made by members of the state legislature and dossiers on each one who was thought to be even remotely persuadable. Warner then sought out each member, working over months to build the kind of trust that would survive a months-long stalemate over the budget.

“If he wanted to see me, he’d pick up the phone — not through any staff person,” said former Virginia House Appropriations Committee chairman Vincent Callahan (R-Fairfax), who eventually disappointed Warner by voting against the deal but later endorsed him for the U.S. Senate. “He’d say, ‘This is Mark Warner. Come over to the mansion and have a drink with me.’ ”

Callahan’s preferred Johnnie Walker Red on the rocks would be waiting for him when he arrived to meet — always one-on-one — with the governor.

When veterans of those days hear about the kinds of negotiations Warner is conducting with the Gang of Six — a conversation over steaks at Warner’s home, aideless meetings called for an hour that drag on for three — it sounds eerily familiar.

“Vintage Warner,” said state Sen. William C. Wampler Jr. (R-Bristol), who supported the 2004 tax deal.

Warner’s strength, they said, comes from an unwavering concentration on getting a deal. He is willing to consider ideas that might anger allies and knows when to shake hands and declare victory, even if he hasn’t won every concession he might have hoped for.

“He knows when you’ve reached the ceiling and anything else would be overreaching,” Wampler said.

Durbin said the current negotiations — with devout conservatives such as Chambliss and Sen. Tom Coburn (R-Okla.) — made him understand why Warner had been effective as a Democratic governor dealing with a Republican legislature.

“If I ever had an important negotiation, in or out of Congress, I’d want Mark at the table,” Durbin said, calling the Virginian “relentlessly focused” and “sensitive to the political realities involved” in the task.

Given the sensitivity of the negotiations, secrecy has been vital. The Gang of Six has held scores of meetings, and Warner and Chambliss have been speaking with each other at least once a day. But, unusually for Washington, few details have leaked out.

“We’re straightforward with each other,” Chambliss said. “We say things without worrying about him repeating it or me repeating it.”

An unfamiliar role

The same characteristics that served Warner well as a chief executive who answered to no one when brokering a deal — he’s demanding, he’s impatient and he applies constant pressure — could alienate Senate colleagues if they come to view him as overeager to put his stamp on major legislation.

“It’s got to be extremely frustrating to him now, where he’s one of 100, coming from when he was number one and running the show,” Callahan said.

Adapting to the Senate — where he is a relatively junior member of a chamber that is notoriously slow — has been difficult at times for Warner. He has said he doesn’t always understand the “theater” that seems to accompany every major issue that moves through Congress.

“It’s a different kind of experience,” Warner said. “I’d never been a legislator before. . . . It’s taken some getting used to.”

But he’s had some success. Warner played a key role in negotiating portions of the Dodd-Frank financial regulatory bill that became law last year, working closely with Sen. Bob Corker (R-Tenn.) in a debate that was characterized by frequent partisan bickering. His willingness to compromise on that measure drew praise from some top Republicans, even if they didn’t all agree with his proposals.

At the behest of Senate Majority Leader Harry M. Reid (D-Nev.), Warner has served as a liaison for Senate Democrats to the business community. His approach to that task is similar to his strategy in the deficit negotiations — hosting small, informal gatherings of the key stakeholders.

Warner will be up for reelection in 2014. If the Gang of Six reaches an agreement that is central to a broader bipartisan deal on deficit reduction, it would help cement his reputation for independence back home and boost his profile in the Senate.

“He’s staked out a position in a way that gets him nationally recognized as a force to be taken seriously on what many people consider the key domestic issue in the country right now,” said George Mason University political-science professor Mark Rozell. “Strategically, it makes perfect sense for him.”