The late Rep. Morris K. “Mo” Udall, D-Ariz., a gentle giant with laughter in his soul and steel in his spine, was the runner-up for the Democratic Party presidential nomination in 1976.

As an admirer and campaign worker for Udall in that race, I was able to observe that, because of his unwavering, self-deprecating humor, he was never able to convince himself — unlike basically every other presidential candidate can — that the very survival of the Western World depended upon his winning the White House. That was just one of the reasons so many of the reporters who covered Udall personally liked him so much.

The great majority of presidential nominees, without ever publicly voicing the words, would probably agree with what President Woodrow Wilson, a lifelong Calvinist, announced on the eve of his own inauguration: “God ordained that I should be the next president of the United States.”

That Udall knew himself and understood leadership was clear from his wise advice about the serious business of picking a president. “Beware,” he warned, “of the presidential candidate who has no friends his own age and confidants who can tell him to go to hell.” Udall undoubtedly had in mind the Democrat who defeated him in 1976, Jimmy Carter, a man without contemporary friends able to tell him bluntly when he was really fouling up. But Udall’s warning is just as seriously true today and for 2016. To be fair, Carter did have in Hamilton Jordan, Jody Powell and Jerry Rafshoon, talented political operatives, but all were staff and a generation younger than their boss.

What brought this to mind was a letter from the Franklin D. Roosevelt Presidential Library & Museum I read that was written on Oct. 8, 1960 — in the heat of a presidential campaign — to vice presidential candidate Lyndon Johnson by James H. Rowe Jr., a close friend of LBJ’s and someone who had worked closely in the White House with FDR.

Teddy White, the poet-laureate of 20th-century U.S. presidential campaigns, wrote accurately that Rowe was one of “that rare strain of men who love American politics without profiting from it.”

Rowe wrote to Johnson, who was going to be either the next vice president or the returning Senate majority leader, about the Texan’s mistreatment of his campaign staff. “I have not seen you pay one compliment, thank one person,” he wrote. “I have seen you do nothing but yell at them. … Maybe you do not know it — I do — the morale of your staff is awful. They are in tears, all of them, they are beginning to dislike you intensely. They cannot do anything right, they don’t dare make a decision about where to hang your clothes even, and they bend their heads and wait for the blows to fall — like obdurate mules who know the blow is coming.”

Rowe then tells Johnson, “It makes me so goddamn mad at you, I’d like to sock you in the jaw.” After urging the candidate to “one day a week, go up and down that plane and tell George Reedy and Bill Moyers and the stenographers … that you appreciate what they are doing for you,” Rowe takes off the gloves. “I have a feeling that at present you are caught between vanity … and a curious lack of self-confidence about your judgment of men.” The letter concludes: “This is probably the end of an old friendship. But somebody has to say these things. And I will say one more thing I didn’t mean to say — lay off that booze.”

It is a tribute to Rowe that he cared enough to be so candid with his powerful, old friend and a tribute to LBJ that Rowe would continue as his trusted confidant.

President Barack Obama is regularly told by opponents, at least some of whom despise him, to “go to hell” and worse. But does Obama have any friends like Jim Rowe from whom he solicits and welcomes that level of brutal honesty? Let’s hope.

Mark Shields is one of the most widely recognized political commentators in the United States. The former Washington Post editorial columnist appears regularly on CNN, on public television and on radio. Click here to contact him, or click here to read previous columns. The opinions expressed are his own.