Ron Wyden doesn’t want to call the director of national intelligence a liar.

The Oregon Democrat is too seasoned a politician for that — and James Clapper’s self-assessment, that he answered in the “least untruthful mannerwhen the senator asked whether the National Security Agency was collecting data about millions of Americans, speaks for itself.

“No, sir . . . not wittingly,” Clapper said, when the answer was clearly — and is now demonstrably — yes.

“When I heard his response, I said, ‘I’ve got more follow-up work to do,’ ” Wyden said with studied mildness when we spoke Thursday.

Did Clapper lie? “I want to leave it at that,” Wyden demurred. Then he added, pointedly: “You cannot have strong oversight if intelligence officials don’t give you straight answers.”

And that is the paradox — the fallacy, even — of congressional oversight in the post-9/11 environment.

President Obama has assured the public that Congress had been “fully briefed on these programs.” Yet, for the most part, lawmakers must face down intelligence officials, and assess their urgent claims of national security, without the benefit of expert staff. In this way, Congress can serve more as useful cover for the executive branch than a true check on it.

Once briefed, lawmakers are captives of their classified knowledge: They cannot disclose what they have been told. Thus, Wyden found himself asking questions to which he surely knew the answer, and was reduced to warning obliquely, as he did in 2011, that “when the American people find out how their government has secretly interpreted the Patriot Act, they will be stunned and they will be angry.”

Edward Snowden, in an instant, was able to achieve what Wyden has been seeking for years: a vigorous, informed and public debate about the proper balance between liberty and security.

“I think this is a long, long, long overdue discussion about these issues,” Wyden told me in his first extended interview since the surveillance story broke. “I wish it had been a debate that had been held several years ago, that the administration had started it years ago.”

Indeed, for all of Obama’s professions that “I welcome this debate” on surveillance, his administration has been more of an obstacle than an enabler of effective oversight and reasonable transparency. Declining to publicly reveal operational details is understandable; refusing to reveal even its legal analysis of surveillance and other anti-terrorism activities is not.

It took the leverage of a pending nomination, John Brennan to be CIA director, for Wyden and colleagues to dislodge in February documents on the legal basis for drone strikes.

Ann Telnaes animation: NSA director James Clapper claims his agency isn't collecting your info. (Ann Telnaes/The Washington Post)

Still secret is the administration’s stretched-to-the-max interpretation of Section 215 of the Patriot Act, which allows the government to seek a secret court order to obtain records relevant to a national security investigation — the very basis for the telephone data vacuuming.

“There’s virtually nothing that limits the government’s authority to collect here,” Wyden told me. “Medical records, financial records, library records, gun purchase records. . . . This basically is a huge sweep of individual records, and it can supersede other laws.”

To read Section 215 is not to understand it in the all-encompassing manner the administration does. Congress authorized intelligence officials to seek court orders when there are “reasonable grounds to believe that the tangible things sought are relevant to an authorized investigation.” But that hardly seems to empower collection, as the Verizon order demanded, of “all call detail records” of all Americans. If the law reaches so broadly, wouldn’t that be worth knowing — and debating publicly?

“What we’ve seen in one issue after another is essentially the practice of secret law, where there is a different interpretation used by the government of the United States than a plain reading of the statute would suggest,” Wyden said. “You can’t have much of a debate with the public if there’s that big a gap between what the public thinks a law means and how the executive branch is interpreting it.”

Or when the executive branch — Wyden won’t say it, but I will — lies to Congress. Wyden advised Clapper’s office a day earlier of his intent to ask the question; he told me there was no push-back from the intelligence director. After Clapper’s testimony, Wyden offered him a chance to fix it. Opportunity declined.

And White House press secretary Jay Carney told reporters this week that Obama “certainly believes that Director Clapper has been straight and direct in the answers that he’s given.”

From “most transparent” (Obama) to “least untruthful” (Clapper). Quite a fall.

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