Just about every party that's ever lost an election has tried to make sense of why it happened. But getting it right is tricky, and maybe not even fully possible. Voters are fickle, one-size-fits-all explanations are elusive, and there's the very human tendency to embrace self-exonerating answers.

For Democrats grappling with how Donald Trump became president, the challenge is even more complicated, since his victory defied so many supposed laws of politics. The stakes couldn’t be higher: Misread the forces at work and the Democrats could end up stuck with him through January 2025.

Hillary Clinton, with her best-selling campaign memoir, has now put forward her thoughts on what happened. Whatever you think of them, she and the campaign she ran in 2016 are central to her party's dilemma. There are two lenses through which Democrats can view her defeat. The one they choose will shape how they tackle bigger questions of strategy, direction and philosophy.

Theory #1: It was Clinton's fault

The narrow lens sees Clinton as a uniquely vulnerable candidate, one whose liabilities — whether deserved or undeserved — enabled Trump to win an election he had no business winning.

In exit polling, for instance, 60 percent of voters said they viewed Trump unfavorably — a toxic number by any historical standard. But 55 percent also had a negative view of Clinton. Similarly, 64 percent of voters called Trump untrustworthy, but 61 percent said the same of Clinton. Her numbers weren’t quite as bad as his, but they weren't far off, either.

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When you factor in how slim Trump's margin was — a combined 70,000 votes in the three decisive states, with a national popular vote deficit of 2.7 million — it raises a possibility: Did Democrats nominate the one candidate not capable of taking advantage of Trump's massive flaws?

If that's what it was, then there's not much wrong with the Democratic Party that a new standard-bearer won’t be able to fix. There's no evidence Trump has built new support since the election, and it's possible he's even suffered defections from his base. There's no shortage of Democrats lining up for 2020; find one even marginally more popular than Clinton and they’ll be poised to unseat Trump.

Clinton and her loyalists pin her negatives on external forces, including Russian meddling and deeply embedded sexism. They also maintain the press radically overplayed her use of a private email server, with James Comey's last-minute intervention inflicting the mortal blow. Even if you accept this, it still sets a relatively low bar for 2020, given that Clinton came within an inch of victory despite all of these hostile forces.

Theory #2: It wasn't about Clinton

Then there's the broader lens, through which Clinton becomes far from the only Democrat who could lose an election to Trump. In this view, Trump has pushed politics away from an ideological battleground and onto a cultural one, creating a new level of polarization that fortifies him in ways that traditional measures don’t fully capture.

This is what Doug Sosnik, a former Bill Clinton consultant, was getting at in a recent opinion piece in The Washington Post that declared Trump, despite his dismal job approval ratings, on course to win again in 2020. "We have entered a new era in American politics," he wrote. "The 2016 election exposed how economic, social and cultural issues have splintered the country and increasingly divided voters by age, race, education and geography. This isn’t going to change."

President Donald Trump at the White House on October 6, 2017. Brendan Smialowski / AFP - Getty Images

Trump’s presidency dominates not only the news but all of popular culture, and the effect is tribalizing, a constant invitation to every American to choose camps. He antagonizes giant swaths of the country, but at the same time provokes heated reactions from his opponents that can have their own alienating effect. It's a combination that practically ensures he has all the right enemies. Even if they have a low opinion of him, how many voters are ultimately with Trump because at least he’s fighting — the news media, Hollywood stars, activist athletes, elite culture?

This interpretation of Trump's rise poses difficult questions for Democrats. It would mean that almost any candidate they run against him would be at risk of suffering Clinton's fate.

Here it's worth remembering that Clinton, for all her weaknesses, still enjoyed clear advantages on paper. In the exit poll, only 35 percent of voters said Trump was qualified to be president, while a majority said Clinton was, and only 35 percent said Trump had the temperament to serve; for Clinton, the number was 55 percent. These gaps alone were thought to be insurmountable for Trump, but they weren't.

Sosnik's analysis raises another possibility: What if other supposedly unique aspects of the 2016 election — like the presence of several independent candidates — turn out to be normal features of Trump-era politics?

The consensus among Democrats, it seems, favors the narrow lens view of 2016. "Resist!" is the refrain among the faithful, with threats of electoral retribution against anyone who even hints at an accommodating posture toward Trumpism. The party is also moving leftward, propelled by a traumatized activist class that is in no mood for compromise or introspection.

This may not hurt Democrats at all, and may even help them.

Trump’s approval rating is stuck in the mid- to high-30s and has never broken 50 percent, and he has no significant legislative achievements. Their base's renewed energy along with a different presidential candidate may be all the weaponry they need. It also seems possible, though, that they’re playing right into his hand.