Opinion | Moderates Win a Round in Britain — But a Larger Battle Against Extremism Looms

The British Labour Party has won its largest majority since the founding of the party over a century ago, securing at least 412 of the House of Commons’s 650 seats. And in an age of populism and polarization, it has done so on a moderate, centrist platform.

The new version of Labour — led by Keir Starmer, a former human rights lawyer who served as the head of the Crown Prosecution Service — may seem reassuringly reminiscent of the consensus of the 1990s and early 2000s, when moderate progressives like Bill Clinton and Tony Blair were committed to liberal economics, liberal democracy and a liberal global order.

But it is too early to celebrate this election as a triumph of the center. There is no clear sign that British voters are any more enthusiastic than voters anywhere else for the socially liberal, fiscally conservative politics that this incarnation of the Labour Party represents. At its heart, this election was an emphatic rejection of a chaotic incumbent. The Conservative Party has been reduced to 121 seats, with two seats left to declare, the worst defeat in its 190-year history. It lost vote share not only to Labour and the centrist, pro-European Liberal Democrats, but also to the hard-right, anti-immigrant Reform U.K., led by Nigel Farage, an ally of Donald Trump.

With the far right ascendant and the Conservative Party battered, Britain has entered new political territory. What centrist forces in Britain have earned is not so much a victory as a brief reprieve; how long it lasts depends on how well they use it.

The Conservatives deserved the rebuke they got. They were in power for 14 years, with little to show for it other than a damaging exit from the European Union. After winning by a landslide in 2019, the party burned through three prime ministers, lurching from the feckless populism of Boris Johnson to the reckless 49-day libertarianism of Liz Truss to the uninspiring technocracy of Rishi Sunak.

After its own disastrous showing in the 2019 election, Labour embarked on a transformation. Mr. Starmer took over from Jeremy Corbyn — a veteran of the party’s left, a critic of liberal economics, free markets and Israel, and a passionate opponent of the U.S.-led global order — and committed the party to reduced public spending and lower debt, no increases to income taxes and backing President Biden’s position on the Israel-Gaza conflict. Mr. Corbyn, who was suspended from the party in 2020, was blocked from standing as a Labour candidate in this election.