There were reports of secret waiting lists to hide long delays in care. Whistleblowers said as many as 40 veterans had died waiting for appointments. And Congress was demanding answers.

Despite mounting evidence of trouble at the Department of Veterans Affairs, Sen. Bernie Sanders, then the chairman of the Senate Veterans Affairs Committee, initially regarded the complaints as overblown, and as a play by conservatives to weaken one of the country’s largest social welfare institutions.

“There is, right now, as we speak, a concerted effort to undermine the VA,” Sanders said two weeks after the story was picked up by national news organizations. “You have folks out there now — Koch brothers and others — who want to radically change the nature of society, and either make major cuts in all of these institutions, or maybe do away with them entirely.”

But the scandal deepened: The secretary of veterans affairs resigned. Reports showed major problems at dozens of VA hospitals. And an Obama administration review revealed “significant and chronic systemic leadership failures” in the hospital system.

Sanders eventually changed course, becoming critical of the agency and ultimately joining with Sen. John McCain, the Arizona Republican, and other colleagues to draft a bipartisan bill to try to fix the veterans health care waiting list.

Sanders’ chairmanship of the committee, his most notable leadership post in the Senate, has become a go-to credential in his upstart quest to win the Democratic nomination for president. He routinely boasts of praise from the largest veterans’ organizations, who lauded his fight to expand benefits. And he frequently speaks of how he helped devise the wait time fix and was able to “crack the gridlock” of Washington, as one of his campaign mailers put it.

But a review of his record in the job also shows that in a moment of crisis, his deep-seated faith in the fundamental goodness of government blinded him, at least at first, to a dangerous breakdown in the one corner of it he was supposed to police. Despite inspector general reports dating back a decade that documented a growing problem with wait times, Sanders, who had served on the committee for six years before he became its head, was quick to defend the agency and slow to aggressively question VA officials and demand accountability.

His major objective as chairman was to expand the menu of veterans’ benefits. It was an ambitious goal, and as with his proposals today for free public college and universal health care, many viewed it as unrealistic. The cost was so high that even Republicans who normally favor more aid for veterans blanched at the dollars involved — while fearing that more offerings would cause even longer waits at the overburdened VA.

“His ideological perspective blurred his ability to recognize the operational reality of what was happening at the VA,” said Paul Rieckhoff, the founder of Iraq and Afghanistan Veterans of America. “The reality was that he was one of the last people to publicly recognize the gravity of the situation.”

The bill he ultimately helped write included a hard-fought $5 billion to hire more medical professionals, a provision Sanders favored. As a compromise, he agreed to a Republican provision to pay for veterans to get care outside the department. It was an approach that some Republican presidential candidates — and a veterans’ organization backed by the billionaires Charles G. and David H. Koch — want to expand on, but Sanders and others have long feared it as a step toward privatization and a shrinking of the agency.

A conscientious objector of the Vietnam War who later voted against the Iraq war, Sanders emerged as an unlikely partner of veterans’ organizations, a relationship that solidified when the Democratic leadership selected him to head the committee at the start of 2013. (Though he is an independent, he belongs to the Senate’s Democratic caucus.)

He began his term by calling in the major groups, such as the American Legion and Veterans of Foreign Wars. “I said, ‘OK, guys, what are the issues you are concerned with. How can we address them?’” he recalled.

Veterans’ advocates involved in those conversations said they were impressed.

“He’s just as you see him in the campaign,” said Garry Augustine, the executive director of Disabled American Veterans. “You sit down with him and he’ll lay it on the table and tells you what he’s thinking, and he wants to know what you are thinking.”

Not only was Sanders uncharacteristically approachable for a senator, they said, but in a time of mandatory budget cuts they found him willing to advocate expensive initiatives on their wish list, from restoring cuts to military pensions to expanding dental care and reproductive health options.

Sanders packaged the proposals into one 367-page “omnibus” bill, with an estimated cost of $21 billion over 10 years — a cost that would lead to its demise.

“It was everything that we in the veterans community had been working for — everything was in there,” said Diane Zumatto, the national legislative director with Amvets, who said it was ultimately “too much” and impractical. “It would never get passed because it was such a huge price tag,” she said.

The bill drew a puzzled reaction from Republican colleagues who found it overly expensive and who bemoaned what they viewed as a lack of compromise and a failure to adequately address the existing waits. In February 2014, the bill fell four votes short of the 60 needed to advance in the Senate. Only two Republicans voted for the bill.

Sanders was not happy. “If you think it is too expensive to take care of veterans, don’t send them to war,” he said at the time.

In the interview last week, Sanders still faulted the Republicans, but acknowledged shortcomings in how he built support for the legislation, his main priority of his first 14 months as chairman. “I take some of the responsibility for that,” he said, “that we did not rally the veterans community as strongly as we should to demand that that happen.”

Less than two months after Sanders’ legislation went down to defeat, the concerns over wait times engulfed the agency in the biggest scandal in its history.

The crisis was tipped off in April 2014 by reports that staff members at the veterans hospital in Phoenix were so overwhelmed that they created off-the-books waiting lists to hide delays in care that stretched for months, while top leaders collected bonuses for meeting scheduling goals.

In the months leading up to the revelations, Sanders’ counterpart on the House Veterans Affairs Committee, Rep. Jeff Miller, R-Fla., had taken a tough tack, holding repeated hearings on the delays and calling for a congressional investigation.

Sanders held a hearing in mid-May, after the scandal broke, at which he implored colleagues to resist a rush to judgment. He devoted a significant portion of the session to asking each veterans’ organization testifying whether the hospital system provided good care. All agreed it did.

During the crisis, Sanders did support the commencement of an inspector general investigation, which later found manipulation to hide long waits was “systemic throughout” the VA.

Republicans on his committee, though, were growing impatient, and they wrote Sanders to demand more hearings, which they said they had been requesting since he began his chairmanship. In the first 17 months, they said, he held “only seven oversight hearings, which did not even begin to address the issues facing the department.” The letter noted that Sanders had not responded to their earlier requests for hearings.

Sanders said in the interview that he was deeply engaged in the troubles of the VA, calling the waiting lists and deceit “an outrage and unacceptable.”

“We had a number of hearings,” Sanders said. He said the high marks he had received from major veterans’ groups showed that key constituents felt he “was doing a very good job.”

In the following months, Sanders negotiated legislation to fix the VA, working with McCain, as well as Miller on the House side, on what became a $16 billion package that passed with bipartisan support.

The final bill, Sanders said, included remnants of his earlier “omnibus” legislation.

In stump speeches and debates, Sanders has lauded those negotiations and the eventual law as a signature achievement of his two years as the committee chairman. He lost the position when Republicans took control of the Senate in the 2014 elections.

The law, meanwhile, has proved to be an underwhelming fix: Wait times, the VA acknowledged last summer, were increasing.