President Ronald Reagan works at his desk in the Oval Office of the White House in 1985. (Scott Stewart/Associated Press)

Barton Swaim is author of “The Speechwriter: A Brief Education in Politics” and a contributing columnist for The Post.

Here’s a general rule of political language: Lines generated to accomplish political objectives aren’t much help in the realm of governance. Even the most memorable ones, having accomplished their original purpose, become useless almost instantly. John F. Kennedy’s famous antimetabole about negotiation, for example — “Let us never negotiate out of fear, but let us never fear to negotiate” — nicely preempted criticisms of a new administration’s foreign policy. But how useful is it as a principle, really?

Another line that pops up again and again in U.S. policy debates is Ronald Reagan’s famous dictum, “Trust, but verify.” Recently, for instance, talk radio host Hugh Hewitt asked Sen. Ted Cruz (R-Tex.) whether he thinks Senate Republicans will stay true to their vow not to hold hearings on Justice Antonin Scalia’s replacement. “I would say my approach to that is reminiscent of Reagan’s approach to the Soviets — trust, but verify,” Cruz said. He went on to say that he’s glad his fellow Republicans have expressed steadfastness on the point but that “every one of us, both presidential candidates and the American people, need to hold [the] Republican leadership accountable.” That use of Reagan’s line sounds to me like a highfalutin way of saying something simple — something like “Let’s wait and see if they really mean it” — but it has the advantage of allowing Cruz to drop Reagan’s name one more time.

“Trust, but verify” entered American usage when Reagan’s adviser on Russian affairs, Suzanne Massie, was preparing the president for talks with Mikhail Gorbachev in 1986. Perhaps Reagan ought to learn a few Russian proverbs, Massie suggested, and the one he liked best was “Doveryai no proveryai” — trust, but verify. Reagan liked it so much, in fact, that Gorbachev expressed annoyance at the president for using it at every meeting.

The line worked brilliantly for Reagan’s purposes. The “trust” part suggested good faith toward the Russians; the “verify” part disarmed the president’s domestic critics, who worried that the administration would commit the United States to a deal the Russians had no intention of honoring. Of course, taken on its own, the phrase is either ambiguous or meaningless: If you trust, you won’t insist on verifying, whereas if you insist on verifying, clearly you don’t trust. But that is precisely why, in 1986, it worked so well.

And why it doesn’t work anymore. “Trust, but verify” is routinely used nowadays as though it were a meaningful principle of negotiation, but it isn’t and never was. Consider the reaction to the Iran nuclear deal last year. Congressional Republicans sharply criticized the deal and the administration defended it, in both cases by reference to Reagan’s borrowed proverb. “President Reagan’s method to diplomatic negotiations was trust but verify,” Sen. James Inhofe (R-Okla.) argued. “This deal has no guarantee of verification.” Rep. Luke Messer (R-Ind.) agreed: “It was President Ronald Reagan who said ‘trust but verify’ during arms-control negotiations with Communist Russia. But, it seems the Obama administration is asking us to trust and then trust some more.”

Obama and his surrogates, by contrast, contended that administration negotiators weren’t just abiding by Reagan’s principle but also exceeding it; they were out-Reaganing Reagan. “This deal is not built on trust,” Obama said after the Iran deal was signed. “It is built on verification.” Colin Powell, speaking in favor of the deal, said he was “reminded of what my former boss Ronald Reagan used to say when he talked to the Soviets, ‘Trust, but verify.’ With respect to the Iranians, it’s don’t trust, never trust, and always verify.” A few weeks later, Hillary Clinton suggested that as president her own approach to the Iranians would be similarly guarded. “You remember President Reagan’s line about the Soviets — trust but verify? My approach will be ‘distrust and verify.’ ”

All this tough talk about distrusting the Iranians is fine, but it’s the sort of language you can use only when you’re not actually negotiating. Notice that Obama and his allies didn’t start talking this way until after the negotiations concluded. And indeed Obama himself has from time to time used Reagan’s line without trying to improve on it. Back in 2009, for instance, speaking at a news conference on the possibility of opening negotiations with Iran, the president said, in part, “One of my famous predecessors, Ronald Reagan, I think said it pretty well when he said, ‘Trust, but verify.’ ” He used the line again to explain his stance vis-à-vis Vladimir Putin.

I do not speak Russian, but the fact that “Doveryai no proveryai” rhymes suggests an expressive or figurative aspect that the translation lacks. In English, anyway, it’s poetry rather than policy or principle: It was never anything more than a rhetorical tool with which a brilliant president accomplished a political and diplomatic aim. Today’s politicos seeking to accomplish their own aims will have to find their own Russian proverb.

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E.J. Dionne: Obama echoes Reagan on Iran