New Mexico Sen. Tom Udall is no friend of limited government.

The Democrat is for runaway “entitlements” and against tax cuts. He supports corporate welfare, and enthusiastically votes to confirm Supreme Court nominees who care little for constitutional constraints on federal power.

But facing his final year in the Senate, the retiring “public servant” deserves recognition for being a consistent skeptic of Washington’s happy talk regarding Afghanistan. And as Udall heads for the door, some devastating investigative journalism offers him powerful ammunition to achieve a bipartisan end to America’s longest war.

An early doubter of “Operation Enduring Freedom,” New Mexico’s senior senator was the only member of the Land of Enchantment’s congressional delegation to react to The Washington Post’s blockbuster series “The Afghanistan Papers.”

In an era when “journalism” often amounts to tweets and sound bites, the newspaper’s exploration of how “U.S. officials failed to tell the public the truth about the war in Afghanistan” is dense and compelling. And getting the truth wasn’t easy. It took “a three-year legal battle” for the Post to secure “release of more than 2,000 pages of ‘Lessons Learned’ interviews conducted by the Special Inspector General for Afghanistan Reconstruction” — conversations that “reveal there was no consensus on the war’s objectives, let alone how to end the conflict.”

Among the findings:

—Victor Glaviano, a combat adviser, called Afghan soldiers “stealing fools” who looted equipment provided by U.S. taxpayers. “He complained to government interviewers that Afghan troops had ‘beautiful rifles, but didn’t know how to use them,’ and were undisciplined fighters, wasting ammunition because they ‘wanted to fire constantly.’”

—“An unnamed Norwegian official (said) … that he estimated 30 percent of Afghan police recruits deserted with their government-issued weapons so they could ‘set up their own private checkpoints’ and extort payments from travelers.”

—Operation Iron Tempest, “a storm of airstrikes by B-52 bombers, F-22 Raptors and other warplanes” targeting “a network of clandestine opium production labs that U.S. officials said was helping to generate $200 million a year in drug money,” was a colossal flop. Many “of the suspected labs turned out to be empty, mud-walled compounds,” and “the U.S. military concluded it was a waste of resources to keep blowing up primitive targets with advanced aircraft and laser-guided munitions.”

As the Post’s series ran, Udall went to the floor of the Senate and delivered a blistering attack on the three administrations that “had no well-formed mission for the war, but fought on anyway, and repeatedly misled the American public.” He tallied the costs — 2,300 men and women killed, 20,000 wounded and more than $2 trillion squandered — and called for “this war to end.”

Hurling thunderbolts against a failed foreign policy is easy for a senator whose party is in the minority and who loathes the occupant of the White House. But Udall isn’t a late entry in this fight. In 2009, less than a year after joining the Senate, he declared, “I do not believe our commitment there should be open-ended. It should be an Afghan-led effort. And with the widespread government corruption we have seen … I do not believe we have a reliable partner in this effort.”

In 2010, he lamented that it was now “over one-hundred-and-nine months into this war and counting. That’s longer than the wars in Vietnam or Iraq. It’s longer even than the Soviet occupation of Afghanistan in the 1980s.”

In 2015, when President Barack Obama announced that forces would stay in The Graveyard of Empires beyond his second term — officially breaking his promise to “end the war in Afghanistan” — Udall expressed concern “that leaving troops on the ground risks American lives and billions of dollars, and distracts us from our broader national security interests in the region and around the globe.”

Nearly 10 months ago, Udall and U.S. Sen. Rand Paul (R-Ky.) sponsored the American Forces Going Home After Noble (AFGHAN) Service Act. It declares “victory,” awards “a $2,500 bonus to all members of the military who have served in the Global War on Terrorism” and establishes “guidelines for withdrawal,” mandating that within “a year, all U.S. forces will be withdrawn.” Shamefully, despite the release of “The Afghanistan Papers,” not one senator has signed on to the Udall/Paul bill.

No matter. After a lifetime on the public payroll — gleefully expanding government’s cost and scope — Udall has an opportunity to compensate, at least partly, for his many misdeeds.

In the senator’s remaining days in office, he should make passage of the “AFGHAN Service Act” his primary mission.