Lindsey Graham officially ended his pursuit of the 2016 Republican presidential nomination on Monday. But it had long been clear that he would not succeed in that mission improbable.

Still, lowly poll numbers and relegation to “undercard” debate status can’t obscure this lasting triumph for South Carolina’s senior senator:

He has consistently given Americans a responsible, well-informed perspective of the challenges facing the nation regardless of poll-standing implications.

Even those who don’t share Sen. Graham’s viewpoints on the various tests of our times should admire his integrity.

For instance, though many Americans are understandably war weary, Sen. Graham hasn’t sugarcoated what he sees as the need for “boots on the ground” against the Islamic State.

While he’s leaving the GOP race, he isn’t abandoning a strong national security message that he sees gaining resonance with other candidates. As Sen. Graham put it during a video released Monday to announce his exit:

“I’m far more confident today that our party will reject the Obama doctrine of leading from behind, and will provide the strong leadership America needs to restore our military, take the fight to our enemies, and do what it takes to make our country safe and preserve our way of life.”

And Sen. Graham has infused comic relief into his arguments on weighty topics.

For instance, during last week’s early-bird debate, he offered this perspective on Sen. Ted Cruz, a “Princess Bride” fan, seeming OK with Vladimir Putin’s intervention in Syria:

“Ted, getting in bed with Iran and Russia to save Assad is inconceivable. Princess Buttercup would not like this.”

Yet Sen. Graham’s brave push for comprehensive immigration reform is no laughing matter as it riles up the party’s base against him. He recognizes the importance of not just border security but the folly of mass deportation. He dares to swim against an unreasoning tide that has swept away too many conservatives on that issue.

Indeed, Sen. Graham has consistently bucked the bitter divisiveness that perpetuates Washington gridlock. He reached across the aisle to forge a senatorial accord breaking the impasse on judicial confirmations, which has been a thorny challenge for presidents of both parties.

Sen. Graham also has been a relentless champion for overdue entitlement reform. Even before moving up after four terms in the U.S. House to his now third term in the Senate, he was sounding the alarm about the inescapable balance-sheet problem presented by swelling retirement ranks and a relative dwindling of Americans paying into Medicare and Social Security.

If more candidates in both parties would deliver such straight talk on this accelerating fiscal train wreck, there would be a much better chance of achieving the political consensus needed for practical solutions.

Certainly Sen. Graham demonstrated his resolve to face another difficult fact Monday when he told CNN of his decision to give up what always was a long-shot White House bid:

“At the end of the day, I’m not going to be competitive in my state. I’m not going to be competitive outside my state.”

Thus, Lindsey Graham is not going to be the GOP nominee for president.

But he is going to persist in stating hard truths. The candidates still in the race — in both parties — should heed his policy insights.

Even more importantly, they should emulate his willingness to tell it like it is.

Sen. Graham should be proud that he stuck up for his principles — regardless of the political cost — while making a spirited run for the nation’s highest office.