WASHINGTON — When Edward J. Snowden risked prison to go public with classified documents about National Security Agency surveillance, he said he wanted to give the public a chance to weigh in on what he considered an excessive intrusion on the privacy of Americans.

It is still unclear whether Mr. Snowden, the 30-year-old former N.S.A. contractor now holed up at a Moscow airport, will escape punishment. But he has succeeded in opening the government spying’s trade-offs between civil liberties and security to the broadest and best-informed public debate in many years, even as intelligence officials are horrified at the exposure of their methods and targets.

Gregory F. Treverton, former vice chairman of the National Intelligence Council, said he found Mr. Snowden’s leaks “reprehensible.” But he said there had been nothing in the past quite comparable to the recent national discussion on government eavesdropping and data collection.

“It is kind of paradoxical that it took Snowden to get to this debate,” said Mr. Treverton, now with the RAND Corporation. “I’m disappointed that neither the intelligence committees nor the administration pushed this debate sooner.”