“She would give many disgruntled liberals who cannot stomach Mr. Wallace’s Moscow axis and still distrust Republicans an excuse to rally to the Truman banner,” she added, referring to Wallace’s friendliness to the Soviet Union.

But Luce said that Democrats, “being men first and Democrats second,” probably lacked “the courage, vision, or intelligence to adopt it.” (Luce, a playwright and former managing editor of Vanity Fair, and the wife of one of the nation’s most influential publishers, Henry R. Luce, was way ahead of her time. It would be 36 years before Democrats made Geraldine Ferraro the first woman to be nominated for vice president by a major political party — and another 36 years before Kamala Harris would be the first woman elected to the post.)

There was reason to be skeptical of Luce’s motives behind the free strategic advice. Just the week before, in a speech at the Republican convention, “the GOP’s glamorous Clare Boothe Luce,” as the Washington Post called her, mocked Truman and called her party’s victory in the presidential election a lock.

“Why is everyone so certain?” she asked on June 21, the opening day of the convention. “For three reasons: our people want a competent president; our people want a truthful president; our people want a constitution-minded president.” She mocked Truman as “the unfortunate man in the White House,” adding, “Frankly, he is a gone goose.” Luce called the Democrats less a party than a “mishmash of die-hard warring factions” — white supremacist “lynch-loving bourbons” on the right, and the “Moscow wing” on the left.

In the weeks leading up to the Democratic National Convention, meanwhile, party members continued to agitate for a change at the top of the ticket. Jeremiah T. Mahoney, a delegate from New York, argued in a letter to his state party chairman that Truman’s nomination would cost other Democrats down-ballot.

Mahoney, a nationally prominent attorney and former judge, wrote that “our dear President Truman, of whom we are all so fond, cannot possibly be re-elected,” and urged the party to continue recruiting Eisenhower to take his place at the top of the ticket. Even though Ike had repeatedly stated that he wouldn’t accept the nomination, Mahoney predicted that if the party nominated him, the general would accept out of “duty” to the country.

By the time the two parties gathered for their conventions that summer in Philadelphia, Republicans still seemed like the one on the ascent. In 1946, they had won both houses of Congress, the first time the GOP achieved that feat since before the Great Depression.

To take on Truman, Republicans nominated New York Gov. Thomas Dewey for president and California Gov. Earl Warren as his running mate: “a dream ticket of two hugely popular governors,” as Truman biographer Alonzo L. Hamby called them.

Democrats, meanwhile, were bracing for a nightmare. Earlier that year, Truman’s bold civil rights proposal — including a federal anti-lynching law, home rule for Washington, D.C., and his announcement that he would desegregate the military — had splintered the party into the “mishmash of die-hard warring factions” Luce had maligned.

On the eve of the party’s convention, many Democrats fretted that Truman was a fatally weak incumbent. It was a continuation of how the political establishment had underrated him his entire career. When Truman became FDR’s running mate in 1944, for example, Time magazine mocked him as “the mousy little man from Missouri.” The taunts didn’t let up after he became president. Another popular one: “To err is Truman.”

“Truman seemed very much alone, cheering himself on in a hopeless cause — an election very few thought he had a chance of winning,” wrote Jeffrey Frank in The Trials of Harry S. Truman: The Extraordinary Presidency of an Ordinary Man, 1945-1953.

A July 1 White House news conference, less than two weeks before the Democratic convention, seemed to epitomize Truman’s falling political stock, when a reporter told him about Luce’s advice that he name Eleanor Roosevelt to his ticket and asked if she would be an acceptable running mate.

“Why, of course, of course,” Truman replied. Then he brought down the house with this postscript: “What do you expect me to say to that?”