The question from an audience member made the three network chiefs bristle:

Why aren't the news media holding the White House accountable like they did during the Nixon/Watergate era?

One of the TV honchos, Susan Zirinsky, had the perfect background to answer.

Just minutes before, she had described how — as a college student working part time at CBS — she was briefly in charge of the empty Washington bureau on Oct. 20, 1973, when news of the “Saturday Night Massacre” began to break: President Richard Nixon had fired the special prosecutor. Forty-six years later, Zirinsky really is in charge at CBS; she was named president of the network early this year.

“We are holding this White House accountable — this is our job every day,” she said, with conviction ringing in her voice.

But it may not seem that way to those members of the public who'd like President Donald Trump's lies and misdeeds to catch up with him the way Nixon's eventually did, but foresee little hope of that.

"You can't compare the eras," Zirinsky said.

As the anniversary of the Watergate scandal’s beginning comes around again — the break-in at the Democratic National Committee headquarters was on June 17, 1972 — investigative journalism’s effectiveness is weakened. The reporting may be every bit as skilled, but the results are greatly diluted because so much has changed in the nation, including its media.

During the Watergate era, as Zirinsky noted, there were three networks. Now, cable news, talk radio, thousands of websites and social media create a polluted firehose-blast of information mixed with disinformation.

"The cacophony," Zirinsky said,"is very hard to break through." (Her remarks came during a panel discussion at last week's "Future of News" conference in New York City.)

Back then, what was said on those three networks — often fed by revelations from The Washington Post’s Bob Woodward and Carl Bernstein — was largely believed.

Much more than now, there was a shared set of facts.

That doesn't mean there was agreement about what to do about those facts, or that there wasn't plenty of political spin and denial. ("I am not a crook," Nixon famously said, though he was.)

But in general, straight news was not relentlessly countered by bad-faith propaganda in the style of Fox News' Sean Hannity. (Recall that Fox News, with all of its intended-from-the-start evils, was founded in 1996.)

News came to citizens from sources they trusted — including their local newspapers. While many editorial pages supported Nixon almost to the end, front pages all around the country were telling people what was happening, blow by blow. Those papers are no longer a major news source in many places. Facebook, though, is.

What's more, as Columbia University Journalism School professor William Grueskin pointed out to me recently, today's situation is not only about how the media has changed.

"The press can do only so much," he said.

"Without an independent judiciary, plus a Congress that's invested in a genuine search for truth, rather than covering for the president, even the most intrepid journalism can slip into the void."

Grueskin mentions, in particular, the Watergate-era judiciary, particularly John Sirica, the district court judge who got defendant James McCord to fess up about the Watergate burglary and who helped compel Nixon to turn over the damaging White House tapes. (The first line of Sirica's Washington Post obituary described him as the judge "whose persistence in searching for the facts while presiding over the Watergate cases led to President Nixon's resignation.")

And this: On July 24, 1974, the Supreme Court unanimously upheld Sirica's order that the president must cough up the Watergate tapes. Two weeks later, Nixon announced his resignation.

Grueskin added that there also was a more upstanding U.S. Senate, as personified by Howard Baker, the ranking Republican on the Watergate committee, who despite initial inclinations became genuinely interested in getting to the bottom of the scandal, exemplified by his famous query: "What did the president know, and when did he know it?"

Today’s journalistic work — David Fahrenthold’s investigation of Trump finances in The Post, Lester Holt’s interview with Trump about why he fired FBI director James Comey on NBC, the many investigations into the Trump administration’s contacts with Russian officials during the campaign — should have made far more difference than it has.

In an earlier era, too, the Mueller Report very likely would have blown a presidency out of the water.

As presidential candidate Elizabeth Warren put it with admirable directness in a recent MSNBC town hall, she was left with three undeniable takeaways after an intense session of reading it into the night:

"Part one, a hostile foreign government attacked our 2016 elections for the purpose of getting Donald Trump elected. Part two, then-candidate Donald Trump welcomed that help. And part three, when the federal government tried to investigate part one and part two, Donald Trump as president delayed, deflected, moved, fired and did everything he could to obstruct justice."

Warren added: "If he were any other person in the United States, based on what's documented in that report, he would be carried out in handcuffs."

Much of what was in the report had already been reported in the press — in The Post, the New York Times, on the network news, and by reporters for ProPublica, BuzzFeed News, Mother Jones and the Wall Street Journal.

But, as Susan Zirinsky put it, it's lost in the cacophony. (Televised impeachment hearings, of course, might change that to some degree.)

What does get through the noise to sway the public may then be lost in an increasingly politicized judiciary — Brett Kavanaugh, anyone? — and the reactions of a venal Senate majority leader and his minions.

By itself, journalism — no matter how proficient or how brave — can’t save us from political corruption at the highest level. It never could.

Just as in the 1970s, the Fourth Estate needs the official branches of government to do their jobs, too.

Sadly, there’s less reason now to believe they will.

| Courtesy Margaret Sullivan, op-ed mug shot.

Margaret Sullivan is The Washington Post’s media columnist. Previously, she was the New York Times public editor, and the chief editor of the Buffalo News, her hometown paper.