It’s happened again: The leader of a mainstream party was given favorable election odds, ran a poor campaign, got trounced on social media and was taught a painful lesson by voters. It’s tempting to ask if they’ll ever learn.

British Prime Minister Theresa May is known as a careful plodder, more technocrat and master-of-the-brief than glad-hander. But she took the biggest gamble possible in politics: She called an election she didn’t have to call in a bid to increase her governing majority. David Cameron did something similar in deciding to put Britain’s membership in the European Union up for a vote last year. Both thought victory was assured and both were punished for their hubris.

It isn’t clear yet if May will lose her job as Cameron did. But the election has big implications regardless — for politics, domestic policy and especially the Brexit negotiations that begin in 11 days.

As the initial exit polls showed a loss of Tory seats on Thursday night, the realization set in that, once again, voters weren’t following the script. The Conservatives ended the night having lost their governing majority and facing a hung parliament; they’re projected to get 318 seats. They will most likely stagger on as a minority government, getting support where they can.

This is miles from the thumping majority May expected. And Jeremy Corbyn’s Labour Party pulled off a historic reversal of fortune from the start of the campaign, when it trailed the Tories by more than 20 percentage points. Labour is expected to add around 35 seats from the 232 it received in 2015, an extraordinary coup. Only a short while ago, union boss Len McClusky was saying that 200 seats would be a good result.

It may seem that Thursday’s election changes little: A Conservative prime minister will still occupy 10 Downing Street and Brexit still means Brexit. But in Britain’s winner-take-all system, a narrow majority can change the landscape significantly.

One immediate question is whether May will continue as prime minister; that’s hard to imagine now. The Conservatives are an unforgiving bunch. But they may decide that with the Brexit negotiations beginning so soon, and with such a slim majority, there’s too much to lose now to succumb to in-fighting and become distracted by another leadership election.

If May stays on, her job will become much harder. The fact of Brexit doesn’t change with this election, but the shape of it almost certainly does. The government will have to rely on parties that disagree with its approach to pass a hugely complex deal — if one is reached at all — through two houses of parliament. That may mean a gentler Brexit; or just a more confusing one.

Assuming May achieves a new trade deal with the EU and a smooth exit in 2019, Bloomberg Intelligence’s forecast is that the U.K. economy will still be 2 percent smaller than had it remained in the EU. With a weakened Conservative government, that may be optimistic.

Where did May go wrong? Set aside her manifesto U-turn, her wooden television performances, the awkward refusal to join the debate, and her overuse of the phrase “strong and stable.” May simply fought a negative campaign. The Tory marketing material that arrived in our home mainly warned of doomsday scenarios under a Labour leadership, in language that was suggestive of a hostile alien landing — it was reminiscent of Hillary Clinton’s warning of Donald Trump’s invasion, which likewise backfired.

In the U.K. election, the scaremongering was even less effective, just as the scaremongering about Brexit didn’t work. Voters don’t like being bullied. Today’s Labour voters, many of them young, don’t remember the socialist experiments of 1970s but are still smarting from the financial crisis. They find Corbyn’s promises of stimulus and spending on services attractive; “nationalization” isn’t such a dirty word to them.

Ultimately, May seemed to harbor the same twin conceits as Cameron, Clinton and even France’s mainstream parties: All underestimated the appeal of their opponent’s message, and all assumed that voter support was sticky — that once you have it, you get to hold it. Like a fading brick-and-mortar retailer, they banked on loyalty that no longer exists.

Today’s voters instead resemble online shoppers. They can move quickly and impulsively, but are also ruthless, inclined to deliver a scathing review, and quick to demand a refund if they aren’t happy. Misreading that was May’s biggest error: She looked at poll figures back in April and saw a stock instead of a flow. With party loyalty at a low in the U.K., as elsewhere, there’s more onus on a leader’s personality, so each one of May’s missteps — and there were many — were magnified.

There’s irony in how May got here. Cameron sought to put an end to Tory divisions over Europe by holding a referendum that would settle the matter, unite the party and keep it in power. When his gamble failed, May inherited Brexit and the party, with its simmering divisions. She called a vote of her own to settle any remaining doubts and strengthen her hand. Her party is still clinging to power — but only just.