The sim­i­lar­i­ties are impos­si­ble to ignore. Both are aging Boomers with long resumes in the strug­gle for social jus­tice. Both have cam­paigned on plat­forms of left pop­ulism that take aim at the rich and pow­er­ful. And both have helped spark social move­ments led by activists 50 years their junior. Yes, Jere­my Cor­byn and Bernie Sanders share much in common.

Labour’s policies were their strongest pull—even, or especially, their most socialist ones.

So, as we sur­vey the rub­ble of the Labour Party’s epic defeat, which saw the largest Con­ser­v­a­tive land­slide since Mar­garet Thatch­er, it’s not unfair to ask: What went wrong? What can the the U.S. Left — and the Sanders cam­paign more specif­i­cal­ly — learn from Corbyn’s loss? And, as the hot takes flood in from Amer­i­can pun­dits with lit­tle under­stand­ing of the British polit­i­cal sys­tem, it is equal­ly impor­tant to ask: What should we not learn from this defeat, as well?

There are three key areas where learn­ing will be essen­tial, and contested:

Staving off char­ac­ter assassination

I knew from my time can­vass­ing for Labour in the UK as well as from read­ing the polls: Jere­my Cor­byn was the most unpop­u­lar oppo­si­tion leader in British history.

Pun­dits will point to indi­vid­ual traits to explain his unpop­u­lar­i­ty, rang­ing from his per­son­al­i­ty (a hip­pie! with no charis­ma!) to his poli­cies (he’s a Com­mie!) to his polit­i­cal allies (he cavorts with ter­ror­ists!) to his base of sup­port­ers (they’re anti-Semi­tes, the lot of them).

But speak with many of the Labour sup­port­ers who hit the doors in this elec­tion, and they will tell you that hatred of Cor­byn was far more amor­phous, more inef­fa­ble, more atmos­pher­ic than this. If you were to ask a giv­en vot­er why they hat­ed Jere­my Cor­byn — and I had the oppor­tu­ni­ty to ask many such vot­ers — they were liable to say: ​“I just do.”

The elec­toral costs of such unpop­u­lar­i­ty were extreme. Accord­ing to one post-elec­tion poll, 43% of respon­dents vot­ed against Labour because of the party’s lead­er­ship, com­pared to just 17% for its stance on Brex­it and 12% for its eco­nom­ic policies.

What could have pro­duced such an atmos­phere of con­tempt? The short answer: a sus­tained cam­paign of char­ac­ter assas­si­na­tion in near every UK tabloid, main­stream news­pa­per and oth­er­wise respectable pub­li­ca­tion against Jere­my Corbyn.

The case of anti-Semi­tism is an instruc­tive one. Most British vot­ers now believe that Cor­byn is an anti-Semi­te, but few can point to an exam­ple of his anti-Semi­tism. Why, then, do they believe it? Because the claim was assert­ed, over and over, in the papers. If Cor­byn weren’t anti-Semit­ic, vot­ers were right to ask, why would so many sto­ries get writ­ten about it so many months in a row? The prophe­cy was self-fulfilling.

Sup­port­ers of Bernie Sanders com­plain about his absence from main­stream report­ing. CNN and MSNBC are liable to throw Joe Biden, Pete Buttigieg and even Eliz­a­beth War­ren onto their chy­ron, but ignore Sanders, despite his con­sis­tent polling near the top of the Demo­c­ra­t­ic field.

But Sanders sup­port­ers appear unpre­pared for the next phase of this process, when he moves back into frame but straight into the crosshairs. It’s been said before but bears repeat­ing: We have seen only a frac­tion of the sto­ries that the press will use to bring down Bernie Sanders.

The U.S. Left needs to pre­pare for this, dili­gent­ly and cre­ative­ly. The Cor­byn camp was far too quick to the bunker: ​“It’s a con­spir­a­cy by the bil­lion­aire media.” That may have been true. But the U.S. Left will need a much more proac­tive strat­e­gy for com­bat­ting such destruc­tive sto­ries and pre­sent­ing an alter­na­tive vision of Sanders’ pro­gres­sive personality.

Sun­light is indeed the best dis­in­fec­tant — only a full-throat­ed chal­lenge to mount­ing con­tro­ver­sy can kill it off. And that chal­lenge may require pro­gres­sive can­di­dates to go on all avail­able media out­lets — includ­ing Fox News — and do it themselves.

Main­tain­ing the coalition

The Labour Par­ty elec­toral coali­tion is strik­ing­ly sim­i­lar to that of the Demo­c­ra­t­ic Par­ty, in both its gen­er­al com­po­si­tion and its direc­tion of trav­el: work­ing-class com­mu­ni­ties with low lev­els of edu­ca­tion and, increas­ing­ly, wealth­i­er city-dwellers with high lev­els of education.

It’s a coali­tion that fell to pieces in Thursday’s elec­tion. The Tory land­slide was a work­ing class wave: the Con­ser­v­a­tive Par­ty broke through tra­di­tion­al Labour-vot­ing work­ing-class regions, for­mer­ly known as the ​‘Red Wall,’ to win scores of new seats.

How did Boris John­son — an Eton-edu­cat­ed, sil­ver-spooned, elite-obsessed Tory — man­age to make such gains against a Labour Par­ty explic­it­ly com­mit­ted to the cause of the work­ing class?

The short answer is Brex­it. The ques­tion of Euro­pean Union mem­ber­ship — or more accu­rate­ly, of whether or not the British gov­ern­ment would go ahead with the ref­er­en­dum deci­sion to leave the EU — cut straight through the Labour coalition.

If the Labour Par­ty had embraced Brex­it and served as its par­lia­men­tary hand­maid­en, the Lib­er­al Democ­rats were wait­ing in the wings to claim the urban mid­dle class­es as their own.

If the Labour Par­ty moved to stymie Brex­it, how­ev­er, they would risk los­ing their Leave con­stituen­cies to a Con­ser­v­a­tive Par­ty that promised to deliv­er Brex­it faith­ful­ly. The Labour Par­ty ulti­mate­ly took the lat­ter risk, and lost pre­dictably as a result.

The good news for Democ­rats is, of course, that the Unit­ed States has no Brex­it. Nor is the Demo­c­ra­t­ic Par­ty threat­ened by an adja­cent chal­lenger like the Lib­er­al Democrats.

But Amer­i­cans do have an issue that close­ly resem­bles Brex­it: the elec­tion of Don­ald Trump.

Many pun­dits will com­pare Boris John­son and Trump, in style as in hair­cut. But the Brex­it-Trump com­par­i­son is by far the more rel­e­vant. A vote for Trump, like a vote for Brex­it, was meant to send a shock to the sys­tem and a mid­dle fin­ger to its polit­i­cal estab­lish­ment. That is why Trump vot­ers, like Brex­it ones, rarely care for the imme­di­ate con­se­quences of their vote choice: the vote was all that mattered.

If pro­gres­sives are search­ing for lessons, then, impeach­ment may be a good place to start: a polit­i­cal strat­e­gy that could ulti­mate­ly turn out to be both myopic and fruitless.

Like call­ing for a People’s Vote, impeach­ing Pres­i­dent Trump could be seen as dis­re­spect­ful to the rebel vote of the 2016 elec­tion, and could deep­en the sense of dis­con­tent that gave rise to Trump in the first place. To keep its coali­tion togeth­er, Democ­rats will need to find a path to détente between its com­pet­ing demo­graph­ics. Impeach­ment alone is unlike­ly to be the answer.

Spin, not socialism

Final­ly, the S‑word.

The com­men­tari­at is already swarm­ing with takes about the per­il of far-left poli­cies. Social­ism, the argu­ment goes, was Corbyn’s Achilles heel. And it is like­ly to be much worse in the Unit­ed States, where the S‑word is wield­ed with much greater psy­cho­log­i­cal pow­er and his­tor­i­cal weight.

The prob­lem with this argu­ment is that it’s wrong. Labour’s poli­cies were their strongest pull — even, or espe­cial­ly, their most social­ist ones: the nation­al­iza­tion of indus­try. A recent poll found 84% of respon­dents sup­port­ed nation­al­iz­ing the water indus­try. In anoth­er, 77% sup­port­ed the same for ener­gy and 76% for rail.

The issue was that, in the end, it didn’t real­ly mat­ter. The raft of poli­cies that the Labour Par­ty ush­ered into its man­i­festo — the stuff of a pro­gres­sive wonk’s dreams, and the hard work of so many bril­liant and cre­ative young pol­i­cy thinkers in the UK — sim­ply did not bring peo­ple to the polls in their favor.

Sim­ply put, social­ism was not too strong an ide­ol­o­gy, but too weak an elec­toral strategy.

No, spin still seems to dom­i­nate our pol­i­tics: dirty, rot­ten spin. John­son ran an out­right cor­rupt cam­paign, dis­sem­i­nat­ing lies, shirk­ing account­abil­i­ty and bank­ing on the like­li­hood that peo­ple wouldn’t care. It turns out that 43.6% of them didn’t — choos­ing to sup­port the Tories anyway.

The lessons from this par­tic­u­lar elec­toral injus­tice are vexed. But one is clear: Plans and poli­cies do not deliv­er majori­ties — even if their details deter­mine how you then gov­ern. To win, then, pro­gres­sive Democ­rats must get off of the page and into the street, with a mes­sage that is as sim­ple as it is emo­tion­al­ly powerful.

Lib­er­al pun­dits are going to stop at noth­ing to swing the Demo­c­ra­t­ic Par­ty back toward the cen­ter — and Corbyn’s loss will be pow­er­ful ammu­ni­tion. Pro­gres­sives can­not sweep it under the rug. The lessons are there, if we are will­ing to learn them. But in this moment of despair, those of us on the Left must keep repeat­ing to our­selves, over and over: We can win, and we must.