Elizabeth Warren, in the final hours of 2018, announced her candidacy for the Democratic nomination for president. She now stands as the first major candidate in a Democratic Party about to hold the primaries that it should have held in 2016.

Among everyone The New York Times says may seek the Democratic nomination, almost all the serious candidates would have been better off running two years ago. That includes Warren, Joe Biden, Kamala Harris, and Cory Booker. Instead the 2016 fix was in: who doesn’t believe Obama pulled Biden aside to say, “Kid, this ain’t your year”? Warren, et al, either had their own come-to-Obama moments or were smart enough to back down with dreams of Clinton cabinet positions dancing in their heads. They reassured themselves they would still have time to run after Hillary wrapped up her eight years in office and before it was Chelsea’s turn.

Bernie likely never imagined he’d do much more than use his primary platform to give air to his signature issues of health care and economic reform. That’s why in the beginning he didn’t run against Hillary so much as alongside her, always gentle on her tender spots like those damn emails. But his message about Wall Street excesses and income inequality resonated. Bernie caught a tailwind, and when he did, we all know via the leaked DNC emails and some tell-alls how the Party took him out of the race using superdelegates, rigged debates, ad buys, and did other dirty tricks. Did you know he honeymooned in Russia?

The primary season was supposed to be little more than a warm-up for Hillary, with her Scooby van listening tour and her book tour and her “debates” with Martin O’Malley playing the role of the Washington Generals. How’d that work out anyway?

While no candidate this year has the power that Hillary held in 2016, the temptation by the Party to rig the primaries again is surely great. Why spend all that money on a long series of ho-hum votes? And why hand Trump footage of Harris calling Warren ineffective in some debate when the winner can be pre-determined? If Dems grant the media, currently operating with the hive mind of a 24-year-old Brooklynite who owes her parents money, too much influence, it’ll be some accomplishment-free shiny object like Beto who Trump will treat as a political chew toy. Give the voters another rigged primary—make it another Her Turn—and you likely give America another four years of Trump.

The Democratic Party in 2016 engineered defeat by not letting the process do what it is designed to do: weed out the weak. Instead, they swept every weakness under the rug: Hillary Clinton was the archetypal 21st-century candidate, a perfectly formed tool of the oligarchy. Never mind the emails, the Clinton Foundation, her warmongering record, and most of all her lack of answers to the questions the electorate wanted answered. The voters knew Obamacare had failed them by not providing health care they could afford and that they’d been left behind in an economy fueled by inequality. People with kids dying in Iraq, Syria, Afghanistan, and elsewhere were unsure why. But meh. Her turn. Deal with it.

These shortcomings would have been exposed during a real primary. Instead they were left to fester in voters’ minds, and Trump happened. Yet the after-action reports on 2016 mention none of this. Instead, Trump supposedly won because of Russia and racist redneck misogynists. Anyone working to elect a Democratic president in 2020 who isn’t willing to consider that by rigging the 2016 primary they ran a weak candidate is foolish. The only answer is a free-for-all primary, where the ideas that roil the Democratic Party, the push and pull of what has come to be called “progressivism,” are allowed time in the sun.

Because if the primaries don’t wash out the weaknesses, Trump most certainly will use his honed predator’s instincts to do it in the general campaign. Did you know Beto’s wife is part of a billion-dollar real estate family in Texas, making him more Jared than caped crusader? The primary needs to poke at Warren’s rise to a position of prominence under the very same system that she now claims is rigged. One commentator described this as “a curious vision coming from a person whose life story, like that of tens millions of Americans who have risen far above their small beginnings, refutes her own thesis. It was curious, also, coming from someone who presumably believes that various forms of rigging are required to un-rig past rigging.’” How does she answer that criticism?

And how much emphasis will voters place on diversity? After years of bleating about it, what should be done with Old White Straight Men like Biden or Michael Bloomberg? Will Sanders’ supporters come home to the Party, or will they remember that Bernie was humiliated, forced to help nominate someone at the Democratic convention whom he clearly loathed? The primaries must above all else settle the question of whether or not Bernie is the divisive element a Democratic party already showing its cracks does not need in 2020.

What will a sharp look at Cory Booker’s time as photo-op mayor of Newark and his warm relationship with Wall Street money reveal? What about Kamala Harris’s complex history of supporting some progressive causes while rejecting others as California attorney general? Why didn’t she prosecute Steven Mnuchin‘s bank? And how much time and money will be wasted on political fluffers like Beto, a guy who lost a Senate race in Texas, one of the most important states in terms of electoral votes?

This is not to over-focus on any one candidate; quite the opposite. It is to point out the kinds of issues that an aggressive, unfiltered, unrigged primary process must address, because nobody in the Democratic Party leadership knows the answers. The challenge is two-fold: how will the candidates handle their past decisions and future plans in front of the public? And how will voters react to those presentations?

No one can win against Trump in 2020 simply by being Not Trump. Never mind the Blue Wave in the House: this is the same map that allowed Republicans to grow their Senate majority in 2018 and to control the Electoral College. Trump is the natural end point of 17 post-9/11 years of keeping us afraid. He is the mediagenic demagogue a country gets when it abandons its people to economic apartheid. He feeds off of being Not Not Trump. Every time someone says “well, that’s the end of Trump,” Trump needs only to top himself with his next tweet and the process restarts.

So let the primaries get rough: the winner will need the experience to rise above Trump while simultaneously standing up to him. To beat Trump is to offer a counter-vision under fire. The primary process has to sort out which of the Democrats looking at the White House might be able to do that. Because if the Democratic Party again does not allow the primaries to do their job, Candidate Trump most certainly will do it for them. Again.

Peter Van Buren, a 24-year State Department veteran, is the author of We Meant Well: How I Helped Lose the Battle for the Hearts and Minds of the Iraqi People and Hooper’s War: A Novel of WWII Japan. He is permanently banned from federal employment and Twitter.