OPINION — It was the summer of “Chinatown” and Elton John’s best-selling album “Caribou.” Top-rated TV shows like “All in the Family” M*A*S*H” were in rerun season. But August 1974 was not lacking in drama cut with pathos.

On Aug. 8, Richard Nixon spoke to the nation, announcing his surrender in the battle of Watergate because “I no longer have a strong enough political base in the Congress to justify continuing that effort.”

It was a stunning defeat for Nixon’s indomitable spirit, since his theme in his 1952 “Checkers Speech” saving his spot on the GOP national ticket had been “I’m not a quitter.”

Twenty-two years later, Nixon used the same words in becoming the first president to resign his office: “I have never been a quitter. To leave office before my term is completed is abhorrent to every instinct in my body. But as president, I must put the interest of America first.”

Wednesday’s anniversary of the resignation will spark comparisons between today’s feckless congressional Republicans and GOP patriarchs like Barry Goldwater who forthrightly told Nixon that his Senate support had crumbled.

Meanwhile, many Democrats are petrified that premature talk of impeachment will jeopardize the party’s drive to win the House and long-shot dreams of taking the Senate.

Hedge fund billionaire Tom Steyer — who is embarked on his own perhaps self-serving petition impeachment drive — complained in a speech last week to left-wing activists, “Not a single person in the Senate Democratic caucus has shown the courage and sense of right and wrong to support impeachment.”

Republicans from Trump on down have ridiculed any mention of impeachment as Democrats behaving like “sore losers.” Of course, that argument assumes that everyone from Hillary Clinton to George Soros has spent decades dreaming about President Mike Pence.

Still a mystery

In truth, we currently have no idea whether any 2019 impeachment drive will be based on ironclad evidence or an expansive analysis of Trump’s tweets. The reason why Nixon comparisons are premature is because no one in politics or the media knows what Robert Mueller’s investigation has discovered.

In a world with more leaks than a rotting rowboat, it is hard to get your mind around the reality that the Mueller investigation doesn’t leak. Everything that we know about his investigation comes from Paul Manafort’s trial; more than 30 other indictments and guilty pleas; reports of subpoenas by the grand jury; self-serving comments by mouthpieces like Rudy Giuliani; and Trump’s desperate, caged-man, all-caps tweets.

That sounds ample, except none of this reveals Mueller’s timetable, how much he has learned about the president’s conduct and business dealings and whether the independent counsel will issue a final report recommending impeachment.

In a sense, it is akin to how Pluto (which should still be a planet) was anticipated before it was actually observed in 1930 by Clyde Tombaugh’s telescope. Pluto’s existence had already been theorized because of a wobble in the orbit of Neptune.

What we are witnessing now are only the perturbations caused by the Mueller investigation. But the hard leak-proof reality is that we simply don’t know where it is all leading. Yet.

Looking back at Nixon’s resignation, it is easy to assume that at the height of Watergate, Americans (aside from a few loyal White House aides) were united in the conviction that the president had to be removed from office.

The truth, though, was more complex than that.

A Harris Poll, conducted little more than a week before Nixon’s resignation, found that 56 percent of Americans thought the Senate should remove the president from office, but 31 percent were opposed and the rest were on the fence.

True, a Gallup Poll taken in early August 1974 found that only 24 percent of the electorate approved of Nixon’s performance in office. But the same poll found that 32 percent of all voters would prefer Nixon as president over his successor Jerry Ford and another 23 percent were undecided.

What is clear is that many conservatives (both Republicans and Southern Democrats) were bitterly split over Nixon until the very end. And it would have been easy for reporters touring rural Mississippi or blue-collar Ohio to interview loyal voters who thought that Watergate was a “witch hunt.”

If Mueller delivers an ironclad case against Trump (admittedly, a big “if”), impeachment and conviction would not require every Republican to turn on Trump. All that would be needed would be roughly one-third of GOP Senate caucus to place greater weight on the evidence than party loyalty.

As Elaine Kamarck, a senior fellow at the Brookings Institution, has been pointing out for more than a year, Trump needs friends in the Senate. And with his quick-trigger insults, Trump has been doing everything to destroy every rationale for supporting him other than fear.

Toothless lion?

But fear of Trump could easily weaken after the 2018 elections.

As many as 10 Senate Republicans, for example, would not have to again face the voters until 2024. Then there are those Republicans (John McCain, Lamar Alexander, Chuck Grassley) who are presumably in their last terms in the Senate. Throw in the two sometime GOP moderates (Susan Collins and Lisa Murkowski), independent figures who sometimes have stood up to Trump (Ben Sasse, Lindsey Graham) and, yes, senators like Marco Rubio who recall Trump’s bitter attacks from the 2016 primaries.

The point is not to handicap a Senate impeachment trial that may never occur. Rather it is to offer a reminder that Trump’s job security may be more imperiled than it might appear from TV coverage of rapturous Republican rallies. That presidential insecurity may — more than anything — explain Trump’s increasingly desperate tweets.