“It’s not about me,” Sarah Palin said as she rode a bus emblazoned with her name in three-foot letters. “It’s not a publicity-seeking tour,” she told her Fox News interviewer, as the cameras rolled.

It was, rather, “about highlighting the great things about America.” Such as: Donald Trump’s digs at Trump Tower and Fox News headquarters in New York — both stops on her “One Nation” bus tour.

Actually, there is a tour underway that highlights the great things about America, but it isn’t Palin’s. It’s the farewell tour of Robert Gates, defense secretary to presidents George W. Bush and Obama, whose work over the past 41 / 2 years has dramatically improved the state of the U.S. military. While Palin played cat-and-mouse with the press corps on Interstate 95, Gates set off on a tour of Asia and Europe, where he is receiving the gratitude of soldiers and the acclaim of allies.

Gates, who remained on the job at Obama’s request, took on sacred weapons programs at the Pentagon, fired ineffective generals, won the surge in Iraq, revived a crumbling war effort in Afghanistan and got Osama bin Laden.

During that same time, Palin quit midway through her term as Alaska governor, then went on to a life of $100,000 speaking fees, reality TV shows and incendiary political speech.

The week’s dueling tours of Gates and Palin show the best and worst in American public life. Both call themselves Republicans, but he comes from the best tradition of service while she is a study in selfishness. He’s self-effacing; she’s self-aggrandizing. He harmonized American foreign policy; she put bull’s-eyes on Democratic congressional districts and then howled about “blood libel.”

It says something about the infirmity of our politics that Gates can’t wait to go home while Palin is again being taken seriously as a prospective presidential candidate.

Palin’s antics since she quit as governor in 2009 are legion: Hunting caribou on her TLC show, cheering for her daughter on “Dancing with the Stars,” stoking the “birther” conspiracy, coining the word “refudiate” and earning millions while specifying “Lear 60 or larger” private jets for her transportation needs.

The bus tour continued the vanity: Crashing the Rolling Thunder gathering in Washington wearing black leather, and securing an audience with Trump over pizza in Times Square.

As usual, Palin’s sincerity was suspect: Though she claimed “I honestly don’t look at states according to when their primaries are,” her tour, by total coincidence, takes her from New Hampshire (where she crowded out Mitt Romney’s official kickoff by having a nearby clambake) to Iowa, to South Carolina. In her interview with Fox, Palin claimed that she didn’t participate in a flattering new movie about her but later confessed that she “did a voice-over” for it.

The tour included signature Palin touches: manipulating the media (she refused to divulge her itinerary, resulting in TV news choppers following her approach into Philadelphia), finding financial gain (she requested “generous donations” to SarahPAC), and lobbing rhetorical grenades (America is “going belly-up,” Obama is “coddling” enemies).

Contrast all of that with Gates, who set a new standard for honesty when, at his confirmation hearing in 2006, he admitted that the United States was not winning in Iraq. At the Pentagon, he brought new openness: He ended the gag order banning coverage of flag-draped caskets at Dover Air Force Base. He hired a journalist, Geoff Morrell, to repair press relations. He penned personal notes to families of fallen soldiers and attended funerals.

Gates brought new accountability, firing top officials over the outrages at Walter Reed Army Medical Center and the mishandling of nuclear weapons. He fought with Congress and the military bureaucracy to redirect funds toward troop protection. His championing of mine-resistant vehicles saved countless lives, and his push for better Medevac in Afghanistan cut the average time-to-hospital for wounded soldiers to 40 minutes from 100.

His unusual frankness continued right into his farewell tour. During his trip, he affirmed that “everything is on the table” for defense spending cuts, spoke in detail about disputes with China, discussed shortcomings in Afghanistan and acknowledged his disagreement with Obama’s decision to attack Libya.

To succeed as Gates has under Republican and Democratic presidents is a rare triumph. But Gates departs with characteristic humility. “The best thing I could do when I get out of here,” he told Politico’s Mike Allen as he began his tour last week, “for at least some period of time, is keep my mouth shut.”

If only Sarah Palin could grasp that.