It's very bad that Donald Trump is raising fundamental doubts about the veracity of the 2020 election and the legitimacy of Joe Biden's victory. But it isn't entirely unprecedented.

That's because Democrats have been doing something similar for the better part of the past four years about the 2016 election. This doesn't at all mean that Trump and leading Republicans are justified in their demagogic and civically poisonous lies — or that Democrats have been just as bad as their counterparts in the GOP. But it does mean that blame for the breakdown in political amity can't be apportioned quite as one-sidedly as many Democrats and left-leaning pundits would prefer.

Our only hope for de-escalation of partisan rancor requires coming to terms with each side's contribution to our present impasse.

Many Democrats have become fond of the "asymmetric polarization" thesis, according to which the primary political story of the past few decades has been the continual radicalization of the Republican Party, with Democrats holding fast to the center left. The theory derives its plausibility from the fact that the Democratic base includes large numbers of ideological moderates — the voters who backed Biden and gave him his decisive victory in the 2020 primaries — while in recent years the Republican base has embraced Trump and other forms of ideological brinksmanship.

But this isn't the whole story of the recent American past. Not only is there an active and influential harder-left progressive wing of the Democratic Party that wants to enact a range of sweeping policy and institutional changes, but leading members of the party and its media champions were provoked by Trump's shocking victory four years ago to embrace a radical form of conspiratorial thinking about how the Republican managed to prevail in 2016.

Instead of honest soul-searching about how and why so many voters in the upper Midwest took a chance on Trump and rejected Hillary Clinton (after many of them had voted for Barack Obama in 2008 and 2012), far too many Democrats began espousing wildly exaggerated tales of Russian interference in the 2016 election, including outlandish (and now debunked) stories of active collusion between the Trump campaign and Russian intelligence services. Blaming nefarious foreign influences was so much more psychologically consoling, and so much better for ratings and voter mobilization, than asking hard questions about the party's declining appeal among working-class voters. So that's what far too many influential Democrats did.

The blame-dodging often took the form of claims about the Trump presidency that anticipated the nonsense that Trump now asserts about Biden. In May 2017, then-House Minority Leader Nancy Pelosi tweeted, "Our election was hijacked. There is no question." On MSNBC, prime time hosts pushed paranoid Russia-related stories nightly for months on end through 2017 and 2018, many of them insinuating that Russia had actively conspired to put Trump in the White House. Some even accused Trump of being a literal Russian asset — a Manchurian candidate placed in the Oval Office in order to do the direct bidding of Vladimir Putin himself. No wonder that by 2019, Hillary Clinton herself had taken to calling Trump an "illegitimate president."

The claims had a powerful effect on public opinion among Democrats, just as Trump's ranting and raving is doing now among Republicans. In March 2018, a YouGov poll revealed that an astonishingly high 66 percent of Democrats believed that in 2016 Russia tampered with vote tallies in order to get Donald Trump elected president — a claim with no more evidence behind it than Trump's current assertions about being deprived of victory by voter fraud.

Now, none of this is meant to imply that the Russiagate conspiracy and Trump's voter fraud conspiracy are equally delusional in all or even most respects. Russia really did work to interfere with the 2016 election (while at most influencing the outcome at the margins). Despite troubling questions (at the time) about links between the Trump campaign and Russian operatives, Clinton conceded the election right away (and only began suggesting later on that Putin had kompromat on the American president). Even with its many legitimate concerns, the Obama administration helped with the transition to the Trump administration (while also empowering various people and organizations in the intelligence community to investigate some of its staff members and nominees).

By contrast, there is no evidence at all of widespread fraud in the 2020 election.

That's an extremely important distinction. But it's not an absolute one.

As Damir Marusic has recently argued in an important essay, U.S. political culture is suffering from a self-perpetuating "disease of delegitimization," in which each side indulges in conspiracies that portray itself as an innocent victim of injustice and the other side as its almost omnipotent perpetrator. "But the other side started it!" say people on both sides, and they can all point to evidence to back up the allegation. Though as Marusic points out, casting blame accomplishes little besides making each side feel even more justified in its grievances. The result is that roughly half the country ends up considering the other half irredeemable — and begins to think of the democratic political system itself as compromised and complicit in the injustice for permitting the other side to win and wield power at all.

The sentence that resonates most ominously in Marusic's essay is one that makes a reference to the collapse of Germany's interwar Weimar Republic without drawing special attention to the fact that it came to an end with the rise to power of the Nazi Party. That's fitting. No one in our politics — including Trump — can be analogized to Adolf Hitler. But the incredibly powerful centrifugal forces of polarization that prepared the way for a radically illiberal form of politics in 1933? With that there are all too many parallels today. Hitler and his henchmen didn't just waltz in and overthrow the government. The republic was brought down by a complex, swirling interplay of mutual provocations among fascists, communists, conservatives, and centrist social democrats over more than a decade. As Marusic writes, "All Germans undermined democracy in Weimar."

This is a point made with a great deal of cogency in another recent and very valuable essay: Aaron Sibarium's "The Weimarization of the American Republic," which begins with a historically literate account of democracy's collapse in interwar Germany and then draws a series of troubling political and intellectual parallels to the present, while also taking a brief detour through the political tumult of the 1960s in order to explain why the thus-far less violent convulsions of our own moment could nonetheless portend a far more destabilizing future.

None of which is meant to imply that Trump's efforts to delegitimize the election are anything less than appalling all on their own — or to deny that they are worse than anything we've seen so far from his opponents. But it is to say that those opponents aren't quite the innocent victims and exemplars of moral purity they like to think they are.

We're all sliding toward political illiberalism together.