After getting off the Capitol trains in the basement of the Capitol, Junior Senator David Vitter (R-LA) talks to staff on the phone while on route to the Republican Senate caucus luncheon on Capitol Hill on Thursday. (Melina Mara/THE WASHINGTON POST)

Sen. David Vitter (R-La.) is suddenly in high demand. His banishment is over, his rehabilitation almost complete. Several years after acknowledging his “very serious sin,” he has successfully adopted a higher profile in the divided U. S. Senate.

Vitter is teaming up with Sen. Barbara Boxer (D-Calif.), the chamber’s leading environmental advocate, to shore up levees and beach fronts from flood risk. He is working with one of the financial industry’s biggest thorns, Sen. Sherrod Brown (D-Ohio), on the latest bill targeting mega-banks and their “too big to fail” status. When he’s not working across party lines, Vitter is throwing his increased seniority around in stronger ways: Last week he vowed to block President Obama’s nominee for Labor secretary until the administration releases documents about voting rights issues in Louisiana.

Now Vitter’s name is atop most lists of possible GOP gubernatorial nominees for Louisiana in 2015 when Gov. Bobby Jindal (R) reaches his term limit.

Some senior Democratic and Republican advisers point to Vitter as the latest example of how — if a senator can outlast a scandal and win reelection — the Senate is a forgiving shelter where “sin” is not in small supply. Vitter was lucky that he had almost 3 ½ years after the revelation of his entanglement with an escort service before he had to face voters again— enough time to work town halls and local fairs.

Others weren’t so lucky. John Ensign (R-Nev.), who fell under investigation for helping the lobbying business of his ex-mistress’s husband, resigned in 2011 when his 2012 reelect became untenable. Larry Craig (R-Idaho), up in 2008, announced he would not seek reelection in late 2007 after pleading guilty to soliciting an undercover police officer in an airport men’s room.

The timing of the revelation may have worked in Vitter’s favor, as did a swing away from Obama’s congressional allies in the 2010 midterms. Vitter won reelection by nearly 20 percentage points, the key step of a dramatic turnabout that seemed unthinkable when he first addressed the cloud of scandal that hovered over him six years ago. Back then, his prospects for political survival seemed bleak as his phone number appeared on the D.C. Madam’s client list, and he made the ritual public apology with his wife, Wendy, at his side.

“I asked for and received forgiveness from God and from my wife in confession and marriage counseling,” Vitter said then.

The revelation led to several years of what other senators and top aides described as a sort of ostracism. Senators didn’t necessarily avoid Vitter, but they didn’t seek him out.

Vitter also kept his head down. He worked to rehabilitate his image back home in one of the smartest or luckiest (perhaps both) twists of political fate in recent years. He was never criminally charged. The Senate Ethics Committee, chaired by Boxer, dismissed the case, finding that whatever the conduct was, it occurred “before your Senate candidacy” in 2004 and “did not involve use of public office.”

Few Democrats will openly forgive Vitter’s alleged actions — he never spelled out what precisely occurred with the madam’s clients — but they say they have found in the reengaged senator someone who is willing to work across the aisle on some issues.

With many senior Republicans guarding their right flank for potential primaries, and a crop of young conservatives preaching ideological purity, that makes Vitter something of a rarity in the Senate.

“We have a lot of work to do, Senator Vitter and I,” Boxer declared a week ago in a conference call with reporters.

Vitter is now the top Republican on the Environment and Public Works Committee, which Boxer chairs. The California liberal and the conservative from Louisiana are polar opposites in their views on climate change, as they are on oil and gas exploration.

But last week, Vitter and Boxer won a unanimous committee vote approving their first bill together, a rewrite of the Water Resources Development Act that reforms how the Army Corps of Engineers does projects.

Vitter, who will help manage the bill’s debate on the Senate floor later this spring, called it “one of the most important and impressive bipartisan bills to come out of our committee, and I thank Chairman Boxer for her leadership getting this done so efficiently.”

Vitter allies deny that his work with Democrats is anything out of the ordinary, or especially strategic. They note that in his first year in the Senate, 2005, he worked with Republicans and Democrats to push for funding for the recovery effort after Hurricane Katrina battered Louisiana, and particularly New Orleans, where he was born and raised.

He also worked with Democrats in 2009 to try to win approval for legislation to allow Americans to purchase cheaper prescription drugs from Canada. Some see a conservative strain of Louisiana populism made famous by Huey Long in the 1930s.

But for much of his eight years in the Senate, Vitter has been marginalized as a member of the Senate’s far right caucus, coming in with a particularly conservative 2004 class of Republicans. The prostitution allegations made him an even less appealing legislative partner.

That appears to be over. Late Friday night, during the marathon debate on the budget, Vitter and another Democratic ally, Brown, won unanimous approval of their non-binding amendment that would end federal subsidies for banks with more than $500 billion in holdings.

The Vitter-Brown partnership, first struck up in 2012, is the kind of odd coupling that used to be common in the Senate. A fierce liberal, Brown won reelection last year and has recommitted to reining in the banking industry. In recent months, Vitter has emerged as perhaps the sharpest conservative critic of large banks, fearful that their continued growth exposes taxpayers to the possibility of another massive Wall Street bailout.

“There is growing bipartisan concern across the whole political spectrum about the fact — I believe it’s a fact — that ‘too big to fail’ is alive and well,” Vitter told Federal Reserve Chairman Ben Bernanke last month at a Banking Committee hearing.

In late February, Brown and Vitter gave back-to-back speeches on the Senate floor announcing that they would soon co-author legislation calling for the largest banks to hold a greater amount of reserve capital.

Vitter has even singled out the views of Sen. Elizabeth Warren (D-Mass.), the liberal firebrand whose 2012 election was vigorously opposed by conservatives, saying his “top concern is actually the same as Mrs. Warren’s.”

It’s hard to call Vitter’s recent efforts a charm offensive. Back-slapping has never been his style, and he does not posses the outsized personality of previous Louisiana senators such as the late Russell Long or John Breaux (D).

But during a recent series of votes, Vitter spent the whole time lingering on the Democratic side of the chamber engaged in cordial conversation with Boxer, Sen. Debbie Stabenow (D-Mich.) and others.

He and Boxer also yukked it up during their hour-long hearing approving the water infrastructure legislation. “This is the way that we should be dealing with legislation,” Sen. Benjamin Cardin (D-Md.) said, thanking Boxer and Vitter.

“It couldn’t have been better,” Boxer said. She asked Vitter to commit to continue working on a bipartisan path to assure the bill makes it through the Senate, House and to President Obama’s desk.

“Absolutely,” Vitter said, echoing the pledge to taking a different path that he made six years ago as he stood apologetically beside his wife. “I know this has hurt the relationship of trust I’ve enjoyed with so many of you,” he then said.

“I will work every day to rebuild that trust.”

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