U.S. Sen. Mark Warner was fired up.

After a four-year crusade for tax and spending reforms to rein in a dangerously high national debt, he was finally getting a seat at the table.

In the aftermath of a 16-day government shutdown sparked by bitter congressional feuds, Warner was one of about two dozen lawmakers tapped in mid-October to hammer out a budget agreement and head off another shutdown.

Warner saw it as a chance to use his persuasive skills and knowledge of fiscal issues to convince the group that a "grand bargain" of entitlement reforms and tax changes would stabilize the economy.

"I absolutely believe this is the biggest security threat to our country. Leaving our kids and grandkids with this giant IOU is un-American," Warner said in an interview in his office.

It was not to be.

The budget committee's two leaders worked out a less ambitious fix - approved by Congress last week - that staves off a January shutdown and sets the budget for two years. But it doesn't address the nation's larger spending and debt issues.

Warner's involvement ended up being a small supporting role - one with some humbling lessons in how to gain clout and temper his aggressive style to get things done.

"Am I frustrated? Yes. But does that mean it's time to give up? Absolutely not," Warner said after the budget deal was struck.

A 59-year-old former governor who made a personal fortune in the cellphone industry before entering politics, Warner has a self-admitted reputation as a hyperkinetic, take-charge executive. Since being elected to the Senate in 2008, he has often chafed at the deferential, slow-moving approach that prevails on Capitol Hill, where egos are huge and seniority carries weight.

After Sen. Patty Murray, who led the Senate negotiators, named Warner to the special budget panel, he waited for marching orders.

None came.

In the meantime, Murray, a Washington state Democrat, and her House counterpart, Rep. Paul Ryan, a Wisconsin Republican, were talking privately and saying little to their committee's members.

The full panel of 29 legislators - which included Virginia's other senator, Tim Kaine - held two public meetings. One expert testified, and each member talked, but there was little debate and no votes.

Not wanting to sit on the sidelines, Warner reached out to Murray and her staff, offering alternative proposals, background information and insight about other lawmakers.

Murray, who viewed him as valuable counsel, had more private conversations with Warner than any committee members other than House leaders, said a Senate staff member close to the negotiations.

"He was one-part advice, one part resource or ideas," the staff member said.

Warner started looking for a way to reach out, using his own network of contacts to connect with key legislators and press his ideas. He urged business executives to tell the negotiators that a larger deal was needed to help stabilize the economy.

Mindful that he didn't want to interfere with Murray's talks with Ryan, Warner kept her advised of every move.

Even with her backing, having private conversations with other legislators can be difficult to arrange. In the Capitol, it requires some finesse just to get in the same room without being seen.

This was the case when Warner sought to meet with House Speaker John Boehner - a Republican not easily available to Democratic senators. The meeting was arranged by Sen. Saxby Chambliss, a Georgia Republican who has worked for years with Warner on debt issues and is a close friend of Boehner's.

The two senators drew little attention as they strolled from the Capitol's Senate wing to Boehner's office on the House side. But just as they reached his suite, the door opened, and out walked the entire House GOP leadership team, including Majority Leader Eric Cantor.

Not wanting to explain to Cantor, a Virginia Republican, why he wanted to talk to his boss, Warner quickly turned his back and knelt down, pretending to tie his shoe as Cantor walked by.

Warner declined to discuss his half-hour conversation with Boehner, saying only that he "wanted to make clear" that if there was a chance for a larger debt deal, many legislators would support it.

Boehner's message to Warner: Talk to Ryan, the House's point man for the negotiations.

After trying without success to arrange a dinner with Ryan, Warner asked a mutual acquaintance outside Washington to intercede. A friend convinced Ryan that Warner's counsel was worth his time, and the two lawmakers dined together Nov. 12 - the evening before the second public meeting of the special House-Senate committee.

Warner declined to discuss their conversation.

"I think the more trusting relationships you can build cross-party, between the two Houses, the better," he said.

Murray praised Warner's low-key activities, saying in a prepared statement that "his work on the budget committee was crucial as we negotiated a bipartisan deal."

"Sen. Warner has earned a ton of respect here in the Senate as someone who is constantly looking for ways Democrats and Republicans can work together to tackle our fiscal challenges responsibly," she said.

The Senate staff member said Warner's years of effort on budget issues helped clear the "caustic atmosphere" and swayed some GOP senators to support the bill.

"He has pretty unparalleled relationships with key Senate Republicans," the staff member said. "What we didn't want to do was spend several months working with Paul Ryan and then have it fail."

Warner's relationships stem from his past efforts, including organizing a bipartisan "Gang of Six" senators who tried to find a way to control the growing national debt - which has grown to more than $17 trillion from $14 trillion since he began working on the issue.

If the government is to slow its growth, he argues, Washington must deal with the rising cost of entitlement programs, including Social Security, Medicare and Medicaid, while also changing tax laws to bring in more revenue.

It became apparent early in the budget negotiations, Warner said, that no large fix was possible - Murray didn't want to touch entitlements, and Ryan didn't want any tax changes.

"I wanted bigger, but it was pretty obvious from Day One that it was going to be pretty hard to get there," Warner said.

Warner's passion for debt reduction was spurred by a 2010 presidential debt commission headed by former Sen. Alan Simpson and Clinton administration official Erskine Bowles. The commission proposed a broad series of changes to reduce the deficit and shrink the national debt: eliminating some popular tax deductions; revamping entitlement programs, including Social Security's retirement age for young workers; and cutting some government programs.

The Simpson-Bowles commission warned that as baby boomers retire in greater numbers, Social Security taxes won't bring in enough money in future decades to pay its bills - unless changes are made.

Simpson, a Wyoming Republican, said he understands why Warner is aggravated.

"He's a facilitator, and he's very frustrated with the loggerheads that would drive any centrist, common-sense person crazy," said Simpson, who served three terms in the Senate before retiring in 1997.

Not enough lawmakers are committed to making the necessary changes, Simpson said. "You think they are reasonable and ready to do hard choices. And they tell you that privately, and then they don't do it. That's the worst part of it."

Warner said the budget bill, which sets a spending blueprint for two years, offers at least the promise of Congress working out a larger deal in the future.

"Here's the thing," he said. "You've got to try to look for silver linings, or this can be a pretty frustrating place."