OPINION — “Jaws” movie posters can go a long way toward explaining politics after the release of the William Barr letter that maybe — or maybe not — accurately summarizes the Mueller report.

Republicans may have been lulled into a false sense of security about Donald Trump’s legal jeopardy, especially with the continuing federal investigations in New York. Eventually most of the Mueller report will be released (or leaked) — and it could hit with a bombshell if Barr baldly misrepresented its contents.

For example, the evidence on Trump’s obstruction of justice could be far more compelling than the Barr letter suggested. In that case, the slogan from “Jaws 2” would be an apt description of the GOP’s fatal overconfidence: “Just when you thought it was safe to go back into the water …”

For some Democrats, the lure of a vast made-in-Moscow conspiracy to explain the Trump presidency proved irresistible. And there was undeniably suggestive evidence, especially after former fixer Michael Cohen said in his House testimony early this month, “So to be clear, Mr. Trump knew of and directed the Trump-Moscow [hotel] negotiations throughout the campaign and lied about it.”

But sometimes connecting the dots creates an unintelligible squiggle rather than a clear portrait of illegal behavior.

Watch: The back and forth on why Mueller’s report hasn’t been released yet

In truth, even if Trump viewed Putin’s Russia as the continuation of Ronald Reagan’s “evil empire,” Democrats would still revile the 45th president for his mendacity, his mocking of the norms of democracy, his maladroit style of governing and his malicious attacks on his critics.

The Democratic reaction to Trump brings to mind the slogan from “Jaws: The Revenge,” the final installment of the shark saga: “This time it’s personal.”

Barring startling new revelations, impeachment is as dead as the concept of a balanced budget, no matter how ardently Betsy DeVos wants to cut funding for the Special Olympics.

As a result, the Barr letter has transformed the theater of Democratic hopes from the House Judiciary Committee to the blue-and-red TV electoral maps on election night 2020. But in assessing the cheaper-by-the-dozen field of Democratic presidential contenders, I believe there should be more emphasis on which candidates are capable of governing successfully, beginning on Inauguration Day 2021.

Justifiable Democratic nostalgia about the presidencies of Barack Obama and Bill Clinton tends to gloss over their missteps during their early years in office, which were the result of inexperience seasoned with a dollop of postelection arrogance.

The Clinton administration, in particular, was conceived in chaos, as the White House Mess came to refer to a style of governing as much as an eating place for top staffers. Bill and Hillary spent so much time after the election assembling the politically pitch-perfect Cabinet that staffing the White House became a rushed afterthought.

The ham-handed rollout of the Clinton health care plan — conceived in secret by Hillary and her team — was emblematic of this well-intentioned, but bumbling, approach to governing.

The result: The shocking Newt Gingrich-led GOP takeover of the House in 1994, which triggered the transformation of the Republicans from the party of business to the party of anger.

The report card on Obama’s first two years in office is far more complicated, since the new president inherited the worst economic collapse since the Depression. But there was also a sense of overreach by the Obama team, symbolized by this 2008 quote from incoming Chief of Staff Rahm Emanuel: “You never want a serious crisis to go to waste.”

The frenetic pace of the Obama administration went far beyond the necessary passage of a 2009 economic stimulus bill. The political wisdom of pressing for the Affordable Care Act in 2010 while the economy was still in shambles can be debated. But in hindsight, it is hard to justify the urgency of House passage of a 2009 cap-and-trade environmental bill that died in the Democratic Senate.

The tea party sweep in the 2010 congressional elections curtailed Obama’s domestic agenda for the remainder of his presidency. And the triumphant Republicans added a renewed fury to politics that, in a sense, culminated in Trump’s presidency.

The point of this history is to remind Democrats as they assess the 2020 contenders that successfully governing from the White House is hard in the best of times. And inheriting the White House after Trump’s poison-pen presidency will be especially difficult.

Please understand — this is not a masked endorsement of Joe Biden. Other White House contenders like Sens. Amy Klobuchar, Elizabeth Warren, Kirsten Gillibrand and Cory Booker boast solid Washington experience. Plus, Washington Gov. Jay Inslee spent nearly two decades in the House.

There is a reason why I haven’t mentioned Bernie Sanders, who has been in Congress since 1991, on this list.

The other part of the equation is that any Democratic president replacing Trump will have a special obligation to heal America. Merely substituting left-wing anger for Trumpian rage is a formula for another scorched-earth presidency.

None of this is designed to explicitly rule out other Democrats with short-lived Washington experience (Kamala Harris, Beto O’Rourke and Julian Castro) or none at all (John Hickenlooper and Pete Buttigieg).

Candidates, after all, are more than walking résumés. And there is a predictive risk in underestimating the power of charisma in presidential politics.

It is worth remembering that the last four presidents who entered the White House with impressive Washington pedigrees (Lyndon Johnson, Richard Nixon, Jerry Ford and George H.W. Bush) were driven from office, resigned in disgrace or defeated by political outsiders.

But this tangled history should not free the 2020 Democrats from explaining how they would govern and how they would repair the deep fissures of the Trump years.

Walter Shapiro  has covered the last 10 presidential campaigns. He is also a fellow at the Brennan Center for Justice at NYU and a lecturer in political science at Yale. Follow him on Twitter @MrWalterShapiro.