“For me, this was opposition research,” Donald Trump Jr. told Sean Hannity on Tuesday night on Fox News. “Someone sent me an email — I can’t help what someone sends me. I read it, I responded accordingly.”

No. That’s not how it works.

Essential to political campaigns, opposition research is nonetheless often misunderstood by people who don’t work on them. “Oppo” has become annoyingly casual shorthand for “anything whatever from whoever, wherever, about the other guy.” (Or, lest we forget, in this case, the other woman.) A generous observer might give Trump Jr., a political tenderfoot, a pass for not knowing this. Presidential campaigns, however, are not job-training programs.

No matter how Trump Jr. thinks political researchers spend their days, opposition research is not a dark art. (I’m not sure I’d consider it any kind of art.) When done well, it’s a thoughtful, directed process of compiling known facts and figures about an opponent’s relevant life and career elements to bolster an argument. But even when done badly, opposition research still has nothing to do with what Trump Jr. did. There are lines that trained and talented political operatives wouldn’t cross. The emails Trump Jr. released Tuesday show he has no idea where they are.

When I joined the Democratic National Committee for the 2004 presidential election, I thought I could approach opposition research through the lens of the scientific method, as I’d studied in the field of sociology. I was there to answer the question, “Why should George W. Bush be defeated?” I would formulate hypotheses and seek evidence from the litany of things he had said and done. That litany came mostly from mundane sources such as Nexis or C-SPAN. Diligently, the research team would compile and cite every piece of data. And then, the data could be packaged in any number of ways: by year, by topic, by state, for an ad, for a fundraiser, for a speech and yes, even to assist the media in their reporting.

I quickly learned that the day-to-day reality of opposition research isn’t always that tidy. Here’s why: When people are invested in your candidate, they want to participate. They have ideas, suggestions, “hot tips.” Phone calls to the main line of the campaign get routed . . . to research. Generically addressed letters and emails get routed . . . to research. Friends of friends of your second cousin’s neighbor’s mail carrier somehow get your mobile number. (I never saw a serial-killer-style missive composed with letters cut from a magazine, but some came close.) However strange the source, everything is read, every voice mail listened to. Occasionally, a staffer might fall prey to a blocked number and be trapped hearing a long, fantastical story, offering only benign “mm-hmm”s while colleagues offer sympathetic looks.

The Post's David A. Fahrenthold explains what opposition research is, and whether Donald Trump Jr. crossed a line. (The Washington Post)

But in a normal campaign, that’s where it stops.

That is what “responding accordingly” means. Despite the constant noise from anywhere and everywhere, opposition research involves focused and supervised work. And I certainly believed then, and now, in adhering to ethical standards regarding sources and methods. If something seemed shady, it was — so we wouldn’t do it.

As the extraordinary news unfolded this past week of the meeting Trump Jr. had with Russian lawyer Natalia Veselnitskaya in June 2016 — and especially after he released the astonishing email chain showing that he agreed to the meeting after being told he could get documents that “would incriminate Hillary” as “part of Russia and its government’s support” for his father’s campaign — a friend and I checked our consciences. “If someone ever reached out to us like that, we’d have . . . called our lawyers. Called the FBI. Right?” “Without question.”

The prospect of responding the way Trump Jr. did is out of the realm of possibility, improbable, absurd. Meeting with a Kremlin-linked lawyer for the purposes of receiving incriminating information about an opponent? Um, yes, that seems shady. It would never have happened in any campaign I’ve worked on — two other presidential campaigns, as well as two gubernatorial races — or any of the best ones I’ve worked against. You don’t have to have years of political experience to reject such a meeting — just common sense.

(And by the way, “Political Opposition Research,” as Trump Jr. wrote in his statement on Twitter, isn’t capitalized. Researchers can be editors, too.)

I’ve seen some suggestions that meeting with a stranger from a hostile foreign nation is appropriate in the name of opposition research. Not on my watch. And not on the watch of professionals I know, red or blue. Political campaigns involve sharp elbows and barbs and anger and fear and even desperation, but I have never worked with any researcher who would exhibit such stunningly, alarmingly poor judgment.

In one way, Trump Jr. is right — he can’t help what someone sends him. I don’t fault him for reading it. But if he believes that he “responded accordingly,” he is gravely wrong. As a nation of armchair criminal defense attorneys debates the many ways Trump Jr.’s meeting was a very bad idea, keep one thing in mind: What he did has nothing to do with opposition research.

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