On Thursday, during their second one-on-one presidential debate, Sen. Bernie Sanders seized on Democratic rival Hillary Clinton for name-checking former foreign policy powerhouse Henry Kissinger.

In their previous Feb. 4 debate, hosted by MSNBC, Clinton had offered up unsolicited praise from Kissinger to burnish her internationalist credentials. “I was very flattered when Henry Kissinger said I ran the State Department better than anybody had run it in a long time,” Clinton volunteered at the time. “Not my kind of guy.” Sen. Bernie Sanders on Henry Kissinger

In their second face-off, Sanders slammed her previous comment, arguing that “Henry Kissinger was one of the most destructive secretaries of state in the modern history of this country.” The resulting fiery exchange not only revealed a deep ideological divide between Clinton and Sanders, but also exposed a split in terms of mainstream political perceptions of the Kissinger legacy.

“I am proud to say that Henry Kissinger is not my friend. I will not take advice from Henry Kissinger,” Sanders added on Thursday. ”And in fact, Kissinger’s actions in Cambodia, when the United States bombed that country, overthrew Prince Sihanouk, created the instability for Pol Pot and the Khmer Rouge to come in, who then butchered some three million innocent people, one of the worst genocides in the history of the world. So count me in as somebody who will not be listening to Henry Kissinger.”

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Meanwhile, Clinton stood by her man so to speak, highlighting one of the least controversial portions of his resume, his diplomatic ties with China. “I think it is fair to say, whatever the complaints that you want to make about him are, that with respect to China, one of the most challenging relationships we have, his opening up China and his ongoing relationships with the leaders of China is an incredibly useful relationship for the United States of America,” she said. Clinton had previously praised Kissinger in her 2014 memoir and de-facto campaign manifesto, “Hard Choices,” during which she fondly recalled watching Kissinger’s 1972 trip to China on television.

There are in essence two Henry Kissingers. There is the respected and influential elder statesman, who shaped U.S. foreign policy as national security adviser and the secretary of state for eight years. He was indeed credited with helping open diplomatic relations with China in 1972, and was awarded the Nobel Peace Prize for negotiating the 1973 Paris Peace Accords, which eventually led to the end of the Vietnam War. The Sanders campaign rapid response on Kissinger is straight fire pic.twitter.com/d8CUNsF3nN — daveweigel (@daveweigel) February 12, 2016

And then there is the other Kissinger, who is far more insidious as far as progressives are concerned: A man who played a significant — and some would argue decisive role — in prolonging the Vietnam War at the needless cost of thousands of American and Vietnamese lives. A man who encouraged former President Richard Nixon to wiretap and intimidate his political enemies. A man who supported the secret bombing of Cambodia and Laos, killing thousands of innocent civilians. A man who masterminded an illegal 1973 coup in Chile and other covert politically motivated military interventions in countries like Rhodesia, East Timor and Argentina.

That Kissinger, in the minds of many progressives, is unquestionably a war criminal.

“The statement ‘Henry Kissinger is a war criminal’ is a statement I’ve been making for many years … it’s not a piece of rhetoric. It’s not a metaphor. It’s a job description,” the late author Christopher Hitchens, who launched a one-man campaign to topple the Kissinger mystique in the early 2000s, once said. His book “The Trial of Henry Kissinger” went a long way towards shifting the conversation on Kissinger from praise of his pragmatic realpolitik brand of foreign policy to intense scrutiny of his secretive and, some would argue, startlingly inhumane, world view. As journalist Seymour Hersh claimed in a documentary inspired by Hitchens’ book, “The dark side of Henry Kissinger is very, very dark.”

And yet, the now 92-year-old has had significant influence in nearly every administration over the last 45 years. Despite being dogged by protesters and the occasional threat of prosecution over his actions while in office, Kissinger has been able to maintain his stature in elite political circles, and despite his image as a hawkish icon, he has enjoyed closer relations with the Clintons than some might suspect.

“Kissinger is a friend, and I relied on his counsel when I served as secretary of state.” Hillary Clinton on Henry Kissinger The Nation, Kissinger played a crucial role in lobbying on behalf of the NAFTA during the first Clinton administration, to the detriment of the health care legislation the then-first lady was promoting. Nevertheless, in a 2014 review of his book “World Order” published in The Washington Post, Hillary Clinton has called Kissinger a “friend” with a “surprisingly idealistic” vision whose counsel she relies on.

In that same piece, Clinton said that Kissinger “checked in with me regularly, sharing astute observations about foreign leaders and sending me written reports on his travels. Though we have often seen the world and some of our challenges quite differently, and advocated different responses now and in the past, what comes through clearly in this new book is a conviction that we, and President Obama, share: a belief in the indispensability of continued American leadership in service of a just and liberal order.”

Ironically, despite her current campaign strategy of touting her working relationship with the current president and expanding on his legacy, in one of Clinton’s private emails that has been made public last year from her tenure as secretary of state, she lamented the fact that her relationship with Obama wasn’t as close as the one Kissinger enjoyed with Nixon. “I see POTUS at least once a week while K saw Nixon everyday,” she wrote to her aides. “Do you see this as a problem?”

Kissinger was also a longtime proponent of the removal of Libyan dictator Moammar Gadhafi. And although Clinton’s role in his eventual downfall may be regarded as one of the most controversial aspects of her legacy at the State Department, she earned praise from her predecessor. “I greatly admire the skill and aplomb with which you conduct our foreign policy,” Kissinger wrote her in a 2012 handwritten note made public earlier this year.

One of Kissinger’s great gifts, which even his detractors have acknowledged, is his ability to flatter his way into the corridors of power, sometimes playing one political side of the aisle against the other. Infamously, he consulted both the Democrats and Republicans in the run-up to the 1968 election and allegedly expected a spot in whichever administration seized power the following January.

His mutual admiration relationship with Hillary Clinton may be calculated, but it’s not paying off in the short term for the Democratic front-runner, since Kissinger’s name is downright toxic to most progressives. And with the 2016 Democratic primary electorate so far looking to not just double down on Obama policies but take them further to the left, the most legendary practitioner of cold-blooded triangular diplomacy may not be the best symbol for a candidate desperate to prove she is not a tool of the establishment. If for no other reason than because Henry Kissinger has been the establishment since roughly 1969 — for better or worse.