You could measure the decline of Fox News by the drop in the quality of guests waiting in the green room. A year and a half ago, you might have heard George Will discussing policy with a senator while a former Cabinet member listened in. Today, you would meet a Republican commissar with a steakhouse waistline and an eager young woman wearing too little fabric and too much makeup, immersed in memorizing her talking points.

This wasn’t a case of the rats leaving a sinking ship. The best sailors were driven overboard by the rodents.

As I wrote in an internal Fox memo, leaked and widely disseminated, I declined to renew my contract as Fox News’s strategic analyst because of the network’s propagandizing for the Trump administration. Today’s Fox prime-time lineup preaches paranoia, attacking processes and institutions vital to our republic and challenging the rule of law.

Four decades ago, as a U.S. Army second lieutenant, I took an oath to “support and defend the Constitution.” In moral and ethical terms, that oath never expires. As Fox’s assault on our constitutional order intensified, spearheaded by its after-dinner demagogues, I had no choice but to leave.

My error was waiting so long to walk away. The chance to speak to millions of Americans is seductive, and, with the infinite human capacity for self-delusion, I rationalized that I could make a difference by remaining at Fox and speaking honestly.

I was wrong.

As early as the fall of 2016, and especially as doubts mounted about the new Trump administration’s national security vulnerabilities, I increasingly was blocked from speaking on the issues about which I could offer real expertise: Russian affairs and our intelligence community. I did not hide my views at Fox and, as word spread that I would not unswervingly support President Trump and, worse, that I believed an investigation into Russian interference was essential to our national security, I was excluded from segments that touched on Vladimir Putin’s possible influence on an American president, his campaign or his administration.

I was the one person on the Fox payroll who, trained in Russian studies and the Russian language, had been face to face with Russian intelligence officers in the Kremlin and in far-flung provinces. I have traveled widely in and written extensively about the region. Yet I could only rarely and briefly comment on the paramount security question of our time: whether Putin and his security services ensnared the man who would become our president. Trump’s behavior patterns and evident weaknesses (financial entanglements, lack of self-control and sense of sexual entitlement) would have made him an ideal blackmail target — and the Russian security apparatus plays a long game.

As indictments piled up, though, I could not even discuss the mechanics of how the Russians work on either Fox News or Fox Business. (Asked by a Washington Post editor for a comment, Fox’s public relations department sent this statement: “There is no truth to the notion that Ralph Peters was ‘blocked’ from appearing on the network to talk about the major headlines, including discussing Russia, North Korea and even gun control recently. In fact, he appeared across both networks multiple times in just the past three weeks.”)

All Americans, whatever their politics, should want to know, with certainty, whether a hostile power has our president and those close to him in thrall. This isn’t about party but about our security at the most profound level. Every so often, I could work in a comment on the air, but even the best-disposed hosts were wary of transgressing the party line.

Fox never tried to put words in my mouth, nor was I told explicitly that I was taboo on Trump-Putin matters. I simply was no longer called on for topics central to my expertise. I was relegated to Groundhog Day analysis of North Korea and the Middle East, or to Russia-related news that didn’t touch the administration. Listening to political hacks with no knowledge of things Russian tell the vast Fox audience that the special counsel’s investigation was a “witch hunt,” while I could not respond, became too much to bear. There is indeed a witch hunt, and it’s led by Fox against Robert Mueller.

The cascade of revelations about the Russia-related crimes of Trump associates was dismissed, adamantly, as “fake news” by prime-time hosts who themselves generate fake news blithely.

Then there was Fox’s assault on our intelligence community — in which I had served, from the dirty-boots tactical level to strategic work in the Pentagon (with forays that stretched from Russia through Pakistan to Burma and Bolivia and elsewhere). Opportunities to explain how the system actually works, how stringent the safeguards are and that intelligence personnel are responsible public servants — sometimes heroes — dried up after an on-air confrontation shortly before Trump’s inauguration with a popular (and populist) host, Lou Dobbs.

Dobbs has no experience with the intelligence system. Yet he ranted about its reputed assaults on our privacy and other alleged misdeeds (if you want to know who spies on you, it’s the FGA — Facebook, Google and Amazon — not the NSA). When I insisted that the men and women who work in our intelligence agencies are patriots who keep us safe, the host reddened and demanded, “Patriotism is the last refuge of the — you fill in the blank.” As I sought to explain that, no, the NSA isn’t listening to our pillow talk, Dobbs kept repeating, “Patriotism is the last refuge of the — fill in the blank.”

Because I’d had a long, positive history with Dobbs, I refrained from replying: “Patriotism is the last refuge of the talk-show host.”

I became a disgruntled employee, limited to topics on which I agreed with the Trump administration, such as loosened targeting restrictions on terrorists and a tough line with North Korea. Over the past few months, it reached the point where I hated walking into the Fox studio. Friends and family encouraged me to leave, convinced that I embarrassed myself by remaining with the network (to be fair, I’m perfectly capable of embarrassing myself without assistance from Fox).

During my 10 years at Fox News and Fox Business, I did my best to be a forthright voice. I angered left and right. I criticized President Barack Obama fiercely (one infelicity resulted in a two-week suspension), but I also argued for sensible gun-control measures and environmental protections. I made mistakes, but they were honest mistakes. I took the opportunity to speak to millions of Americans seriously and — still that earnest young second lieutenant to some degree — could not imagine lying to them.

With my Soviet-studies background, the cult of Trump unnerves me. For our society’s health, no one, not even a president, can be above criticism — or the law.

I must stress that there are many honorable and talented professionals at the Fox channels, superb reporters, some gutsy hosts, and adept technicians and staff. But Trump idolaters and the merrily hypocritical prime-time hosts are destroying the network — no matter how profitable it may remain.

The day my memo leaked, a journalist asked me how I felt. Usually quick with a reply, I struggled, amid a cyclone of emotions, to think of the right words. After perhaps 30 seconds of silence, I said, “Free.”

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