Aaron David Miller is a senior fellow at the Carnegie Endowment for International Peace and author of "The End of Greatness: Why America Can't Have (and Doesn't Want) Another Great President." Miller was a Middle East negotiator in Democratic and Republican administrations. Richard Sokolsky is a nonresident senior fellow at the Carnegie Endowment for International Peace and former member of the US State Department's Office of Policy Planning. The opinions expressed in this commentary are those of the authors; view more opinion articles on CNN.

Aaron David Miller

Richard Sokolsky

(CNN) Friday's testimony by former US Ambassador to Ukraine Marie Yovanovitch and President Donald Trump's threatening tweets -- sent while she was testifying -- provide a devastating window into the administration's preternaturally destructive campaign to politicize the Department of State, undermine US diplomacy, and smear the reputations of career State Department officers for upholding the oath they take to defend the Constitution and American national interests.

Together, we have over 50 years of service at the State Department under both Republican and Democratic administrations and have never experienced anything like the travesty that's now taking place. Here are our takeaways.

McCarthyism redux

Not since the McCarthy era of the 1950s has there been as determined a campaign to undermine and discredit career State Department officials. Back then, some 81 officials were forced out of the department amidst charges of disloyalty as alleged communist sympathizers. Secretary of State John Foster Dulles refused to stand up for his people then. And now, Secretary of State Mike Pompeo is also not backing up his team in what former Deputy Secretary of State William Burns has described as an act of "profound political cowardice."

But today's attacks are worse than McCarthy's: they are being actively orchestrated by the President of the United States, who has shown nothing but contempt for the State Department, diplomacy, and America's professional diplomats.