What is it about Henry Kissinger that has put him back on the charts?

Of all of the foreign-policy subplots of this election cycle, it's the one about Henry Kissinger that is the most surprising.

He made his first cameo in a Democratic primary debate between Hillary Clinton and Bernie Sanders, when the latter excoriated the former for talking to the former secretary of state from time to time. Sanders's backers pushed this point to the hilt in the immediate aftermath, generating a few favorable stories but little effect in the polls.

Then, in May, came reports that Kissinger had met with Donald Trump. Trump said later that these conversations hadn't changed his mind on anything. He also said that Kissinger had been converted to the real estate semi-mogul's approach to foreign policy — a claim Kissinger flatly contradicted.

Finally, as Trump continued to immolate himself on the campaign trail and as other senior GOP foreign policymakers came out against Trump, there were reports that Hillary Clinton's campaign was working hard to secure Kissinger's endorsement. This news provoked another strong reaction from the left (and a ghost from the right) and seemed to symbolize their concerns about eroding leverage over Clinton. The New York Times reported:

"Mrs. Clinton's dogged pursuit of Republican votes has especially rankled progressives, and highlights the divisions within the Democratic Party, even as they see a victory more likely. They have grumbled at her eager promotion of endorsements from veterans of the George W. Bush and Reagan administrations, including that of John D. Negroponte, a top diplomat and intelligence official under Mr. Bush. They worry aloud that Henry Kissinger, of whom Mrs. Clinton has often spoken fondly, could be next."

Now might be the moment in this post when readers would expect a vigorous defense of Kissinger's foreign-policy acumen. Well, you'll be disappointed. I do think Kissinger's counsel on the Pacific Rim would be worth a listen, but I wouldn't trust a single thing he says when it comes to Russia, for example.

No, I'm more interested in the larger question of why Kissinger, 40 years after being in power, still generates these kinds of passions. I'm not making any excuses for Kissinger's behavior. But other former policy principals have endorsed … let's say "problematic" policies without anywhere near this level of opprobrium. What is it about Kissinger that inspires such sustained hostility?

The second thing is that Kissinger has displayed zero remorse for his role in his more unsavory policies. John Lee Anderson related an interesting anecdote in the New Yorker a few days ago:

"In Errol Morris's remarkable 2003 documentary 'The Fog of War,' we saw that [former secretary of defense Robert] McNamara, who was an octogenarian at the time, was a tormented man who was attempting to come to terms, unsuccessfully, with the immense moral burden of his actions as the U.S. defense secretary during Vietnam. McNamara had recently written a memoir in which he attempted to grapple with his legacy. Around that time, a journalist named Stephen Talbot interviewed McNamara, and then also secured an interview with Kissinger. As he later wrote about his initial meeting with Kissinger, "I told him I had just interviewed Robert McNamara in Washington. That got his attention. He stopped badgering me, and then he did an extraordinary thing. He began to cry. But no, not real tears. Before my eyes, Henry Kissinger was acting. 'Boohoo, boohoo,' Kissinger said, pretending to cry and rub his eyes. 'He's still beating his breast, right? Still feeling guilty.' He spoke in a mocking, singsong voice and patted his heart for emphasis."

Despite Niall Ferguson's best efforts in "Kissinger: 1923-1968: The Idealist," I'm skeptical that this Kissinger will generate much sympathy from his critics.

The final and most important reason for this enmity is that despite this rising tide of calumny, Kissinger's reputation and influence has persevered. He was the pioneer in developing the post-government consulting shop as a means to make money and still exercise influence. The pursuit of his endorsement in this election cycle is one data point that his voice still counts. The fact that international relations scholars still rank Kissinger as the most effective secretary of state in the past half-century is another. And, indeed, in my own survey of more than 200 members of the foreign-policy elite that I conducted earlier this year, Kissinger was ranked as the person who "exercised the most influence over America's foreign-policy debates."

So all of this enrages Kissinger's critics. I wonder, however, whether Kissinger's reputation will continue to stay so elevated. Part of the reason he has maintained his status is his personal schmoozing of those in power. As that fades from view, history will prove a more astringent crucible. An honest take of Kissinger's foreign-policy record would have to acknowledge his strengths. Increasingly, however, his weaknesses will come into public view.