Sen. John Walsh, right, and son Michael leave the Old Senate Chamber on Capitol Hill after a swearing-in ceremony with Vice President Biden. (Lauren Victoria Burke/Associated Press)

This was supposed to be Sen. John Walsh’s big week on Capitol Hill, leading the charge on a tax-break bill for manufacturing companies aimed at bringing jobs back to the United States. It would be the first major bill for the Montana Democrat, who was appointed to the Senate just five months ago and now finds himself and locked in an uphill battle to win a full term this fall.

Instead, Walsh’s introduction to many voters back home turned disastrous as Montana papers Thursday blared unhelpful headlines: “Walsh plagiarized final paper for college degree” and “Walsh plagiarized thesis.”

The 53-year-old political neophyte, a former Army commander who saw heavy combat in Iraq, also revealed for the first time that he suffered from post-traumatic stress disorder related tohis war service. While the senator avoided the spotlight Thursday, his staff tried to minimize the fallout and steady the campaign to retain his Senate seat after a Wednesday New York Times report about extensive plagiarism in an Army War College paper.

In a four-page memo, Walsh campaign officials tried to reintroduce the senator to voters, trying to emphasize his credentials as a military leader and as a regular guy without a fancy degree.

“He’s a great soldier, who learned war strategy on the battlefield firsthand but he’s not a classroom academic — the Senate already has plenty of those,” Lauren Passalacqua, Walsh’s campaign spokeswoman, said in the memo.

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Walsh’s nonpolitical biography — soldier, leader, hero — was a reason he soared so quickly in the polical sphere. But he has become a cautionary tale about novice candidates who rise quickly without the appropriate vetting.

His aides backtracked from the initial suggestion that his PTSD played a role in his appropriation of about a quarter of a 14-page dissertation on Middle East policy — the final paper required for his master’s degree — that did not credit the sources. The campaign team described it as an “unintentional mistake”.

While Republican campaign operatives assailed his plagiarism as disqualifying, Democratic colleagues stood behind him.

“I think that stacked up against his record in Iraq, his record in the National Guard, and his service to Montana, I think voters will understand that full picture,” said Sen. Michael F. Bennet (Colo.), chairman of the Democratic Senatorial Campaign Committee.

Sen. Jon Tester (D-Mont.) said it was a “hiccup” that would not be a determining factor in Walsh’s race against Rep. Steve Daines (R-Mont.). Democrats said the race had grown a bit closer since the little known Walsh was first appointed, when he trailed badly.

“A soldier’s not an academic, you know. He’s a great guy, I’m going to tell you. He’s as straight up and nonpolitical as anyone I’ve ever served with,” Tester said.

Walsh spent Thursday avoiding questions about his actions. In the morning, he presided over the Senate for a two-hour shift, a ceremonial role rotated among junior members of the Democratic caucus.

Walsh swayed back and forth in the president’s chair, sometimes texting on his phone and sometimes reading intensely. He chatted with Sen. Charles E. Schumer (D-N.Y.) and, later, with Majority Leader Harry M. Reid (D-Nev.). Then he quietly ducked out of the Senate chamber.

Later in the day, Walsh reentered the Capitol to attend a caucus lunch, avoiding the underground subway entrance where reporters had camped out to wait for him. He instead approached the gathering from a side staircase, walking with his phone pressed to his ear.

A string of seemingly random events thrust Walsh into this spotlight, any one of which could have gone differently.

After receiving his master’s degree from the Army War College in 2007, Walsh was appointed adjutant general of the Montana National Guard, making him the state’s top guardsman under then-Gov. Brian Schweitz­er (D).

As the 2012 race to succeed Schweitzer heated up, Democrat Steve Bullock was drawn to the Bronze Star winner’s nonpolitical background. With more than 100,000 veterans living there, almost one in five Montana voters could have military experience. So Bullock picked Walsh as his running mate, ending his 33-year career in the military. After a narrow victory, Bullock and Walsh took office in January 2013 as governor and lieutenant governor.

Then, a few months later, Sen. Max Baucus (D-Mont.) rocked the state by announcing that he would retire, instead of seeking a seventh term. No fewer than six Democrats considered entering the race and declined, including Schweitzer.

Democrats in Washington were drawn to Walsh’s biography, thinking that he could win by running as an outside-the-box candidate. Walsh jumped into the race, the first time he had run for office.

Then Baucus shook Montana again, agreeing to his nomination by President Obama to become ambassador to China and leaving the Senate in February. Reid urged Bullock to name Walsh, thinking that eight months as an appointed senator would help him build name recognition and boost his chances of victory.

The governor told Reid to back off, but weeks later he sent Walsh to Washington to fill the final 10 months of Baucus’s term and run in November as the incumbent.

Early polling had Walsh trailing by as much 15 percentage points, but some recent polls showed the race within five to seven percentage points.

Reid’s leadership team assigned to Walsh the legislation aimed at luring manufacturing jobs back to this country, a role designed to appeal to voters even though the measure is probably headed into a Republican filibuster over procedural matters.

Reid set the schedule so that this would be Walsh’s week. There were conference calls with news media last week to promote the legislation, and Capitol news conferences were scheduled for this week to place Walsh at center stage.

On Tuesday, Walsh skipped a news conference on the issue. Later, he called Tester to tell him what the New York Times was about to report.

“He’s an Iraqi combat veteran who saw some crap that none of us should have to see,” Tester said, “and he survived it, and he’s moving forward with his life.”