Correction: The original version of this story referred to Sen. Jack Reed (D-R.I.) as a Vietnam veteran. Reed was in the U.S. Army during the Vietnam War but did not serve in Vietnam. This version has been updated.

Virginia Gov. Tim Kaine, left, stands on stage with Democratic presidential candidate, Sen. Barack Obama D-Ill., and Sen. James Webb, D-Va. during a campaign event at the Nissan Pavilion in Bristow, Va. Thursday, June 5, 2008. (Alex Brandon/ASSOCIATED PRESS)

James Webb is leaving Washington — official Washington — again.

Virginia’s 66-year-old senior senator has never stayed in any government job — including Marine Corps officer, House committee lawyer, assistant defense secretary and Navy secretary — for more than about five years. So, right on cue, in early 2011, after reaching the five-year, one-month mark in his term, the Democrat announced that he would not seek reelection.

No shock, there. But the real questions remain: Will he ever return? And what has he accomplished?

“I came here to help govern rather than having a specific laundry list,” Webb said in an interview in a narrow conference room adjoining his Senate office, identifying the themes that have defined his tenure: economic fairness and social justice, reorienting national security policy, and reestablishing the balance of power between the legislative and executive branches.

All three have been long-standing concerns, whether stemming from Webb’s time in Vietnam, his service as a Capitol Hill staff member, or his abiding interest in the history of his working-class, Scotch-Irish forebears. So Webb refuses to measure success based on what he does or doesn’t accomplish before his successor is sworn in.

“This isn’t going to end just because I’m leaving office,” he said. “I used to write regularly about these issues . . . and I will continue to work on them.”

In some ways, Webb was incapable of settling in on Capitol Hill. He is a senator who hates the glacial pace of the institution, a candidate who toppled a Virginia legend but is an unenthusiastic campaigner, a Democrat who occasionally exasperated — and was exasperated by — his own party.

These differences, his admirers say, will be missed. “The Senate,” said Sen. Mark R. Warner (D-Va.), “doesn’t need everybody to be out of the same cookie cutter.”

A mixed record

Webb has scored some notable achievements in the Senate, particularly passage of the post-Sept. 11 GI Bill. He also helped establish a high-profile commission on wartime contracting that found that tens of billions of dollars were wasted in Iraq and Afghanistan because of lax oversight.

But Webb’s long push for a panel to study ways to reform the criminal justice system was stymied last fall, when Senate Republicans blocked a measure despite bipartisan sponsorship and the support of a wide range of organizations.

His calls for Congress to reassert its role in deciding when the United States sends its military into harm’s way have mostly fallen on deaf ears, despite a brief burst of attention last year during hostilities in Libya.

“I think the Senate needs to step up in terms of regaining its proper constitutional authority, and I think that’s Republican or Democrat,” Webb said. “That’s where the institution has kind of atrophied.”

Between those two poles, he has scored successes that are more difficult to measure.

Economic fairness, a longtime theme in Webb’s writings and his 2006 successful campaign against then-Sen. George Allen (R), has become a staple of Democratic rhetoric and a key plank in President Obama’s reelection efforts. Webb signaled this priority three weeks after he was sworn in, when he delivered the Democratic response to President George W. Bush’s 2007 State of the Union address. In it, he cited a favorite principle from President Andrew Jackson — “that we should measure the health of our society not at its apex, but at its base.”

“Against some advice, and [Senate Majority Leader] Harry Reid will be happy to confirm that,” Webb recalled with a laugh, “I wrote my own speech and put economic fairness at the top of it. We forced that issue.”

On foreign policy, Webb has helped push the nation toward its recent strategic pivot to Asia, combining increased military resources in the region and enhanced partnerships with the countries that ring China.

“We’ve become the office up here in terms of the reconnection with East and Southeast Asia,” Webb said. “We led that.”

Senate Armed Services Committee Chairman Carl M. Levin (D-Mich.) said Webb has been “very influential” on Asian policy, and Sen. Jack Reed (D-R.I.), another committee member and fellow veteran, made a similar point.

“He’s taken a real keen interest and it goes back decades, and the interest is both to recognize the emerging strategic and economic impact of Asia, and do it in a thoughtful way,” Reed said.

When the United States restored diplomatic relations with Burma this year, a senior State Department official singled out Webb in a background briefing for reporters.

“He has pioneered many of these actions,” the official said. “He was one of the first senators on the ground pushing for the release of political prisoners, asking for the United States to engage actively. And I think [Secretary of State Hillary Rodham Clinton] wanted me to underscore our gratitude for his service not only in the Senate but basically as a diplomat in the Senate, and that has been significant.”

At times, Webb seems more likely to talk about water rights on the Mekong River and stability in the South China Sea than the James River or the Chesapeake Bay. Unlike many colleagues, he does not appear concerned about ginning up good press back home.

“It’s not glitzy stuff,” he said. “It’s not the kind of thing you’re going to see on a talk show, but we’ve made enormous contributions in that area.”

‘Doesn’t really fit into either party’

Webb does make headlines — and sometimes the kind that lead to headaches for fellow Democrats. Republicans frequently invoke his departures from party orthodoxy to criticize Obama and, more recently, Timothy M. Kaine (D), who is running against Allen — Webb’s 2006 foe — to replace Webb.

A typical release issued in April by the National Republican Senatorial Committee was headlined: “Webb’s straight talk to Virginians continues to stand in stark contrast to Kaine’s unabashed support for Obama.”

GOP operatives regularly cite Webb’s long-standing opposition to raising taxes on ordinary earned income, which means — unlike Obama and Kaine — he wants all of the Bush-era tax cuts that are set to expire to be extended. But Republicans typically ignore the fact that Webb supports increasing capital gains taxes.

“The position that I have [on taxes] is heartfelt and it doesn’t really fit into either party, I don’t think,” he said.

Webb also has been used as a cudgel against the White House on health-care reform. Although he voted for the landmark legislation when it passed the Senate, he drew notice in April for saying that Obama’s handling of the issue “cost him a lot of credibility as a leader.”

Although Webb is a former Republican, he is not going to follow the path of neighboring Sen. Joe Manchin (D-W.Va.), who has said he’s not sure whether he’ll vote for Obama in November.

“I’ll support President Obama,” Webb said.

He does acknowledge that he has had “a lot of differences with the administration” on various issues. (He recently criticized the White House for delaying oil and gas exploration off Virginia’s coast).

In particular, Webb thinks Obama needs to do a better job of connecting with white working-class voters, a demographic Webb has analyzed in his book “Born Fighting” and in numerous op-ed pieces.

“I think this is a challenge for the entire Democratic Party and I’ve said it many, many times,” he said.

Webb thinks Obama can win Virginia again if he can replicate the historic turnout of 2008. He is more bullish about Kaine, predicting that he will defeat Allen by five percentage points in November and scoffing at GOP efforts to draw differences between the two Democrats.

“Tim Kaine and I have a great friendship and I’m really gonna do my best to help him get elected,” Webb said.

As for whether Allen has changed much since their hard-fought 2006 campaign, Webb said only: “I really haven’t watched him.”

Looking ahead

Has Webb enjoyed the Senate? That may be the wrong way to frame the question.

“It’s been very fulfilling,” he said. “I didn’t come here to have fun. I came here to try to serve in the same sense that I went into the military to try to serve. I think we’ve had a sense of purpose every day, and that’s what counts.”

Satisfying as the job has been, Webb has no regrets about his decision to leave.

“We thought about it really hard,” he said. “This is the fourth time I’ve been in public service, and each time after I’ve been in public service for a while, I’ve left and done other things. I think it’s healthy. I think it’s healthy intellectually, and I think there’s a synergism in it.”

Webb makes clear that he does not have his next step sketched out. “I don’t know. I didn’t even announce for the Senate until nine months before the election, so I don’t plan long-term,” he said.

Given his pronounced interest in Asia — and the fact that he speaks Vietnamese — a foreign policy post could be a fit. He has previously laughed off a question about whether he is interested in being secretary of state by noting, “The job is already filled.”

But will Webb return to government service — in or outside of Washington?

“I would hope he stays involved in public service,” said Sen. Charles E. Schumer (N.Y.), one of the chamber’s Democratic leaders. “He’s very passionate about a lot of things, and my guess is he will.”

In the meantime, the obvious immediate move is a return to writing. Webb has penned novels, nonfiction books, screenplays, newspaper articles and has said he will work on the same handful of issues that have fueled his Senate tenure.

“I think first and foremost he thinks of himself as an author,” Warner said. “You finish a chapter and you move on to a different chapter. I’m sure he’s got more chapters to write.”