A dramatic victory in a parliamentary special election. Hundreds of seats won in English municipalities. A first taste of power in the lower tiers of government.
By making extensive gains in a set of local elections held in England on Thursday, Nigel Farage, one of Britain’s best known supporters of President Trump and the leader of the anti-immigration Reform U.K. party, consolidated his reputation as the country’s foremost political disrupter.
But he may have done something bigger still: blown a hole in the country’s two-party political system.
For nearly all of the past century, power in Britain has alternated between the governing Labour Party, now led by Prime Minister Keir Starmer, and the opposition Conservatives, who last year selected a new leader, Kemi Badenoch.
Yet with surging support for Reform and gains for other small parties, that duopoly has rarely looked more shaky.
“The two main parties have been served notice of a potential eviction from their 100-year tenures of Downing Street,” said Robert Ford, a professor of political science at the University of Manchester.
Still reeling after being ejected from power last year, the Conservatives suffered another disastrous set of results. With the economy flatlining, Labour was punished by voters angry with government spending curbs and higher taxes introduced since it came to power.
The electorate rejected both main parties, Professor Ford said, adding that, were a result like this to occur in a general election, “the Conservative Party would cease to exist as a meaningful force in Parliament.”
Claire Ainsley, a former policy director for Mr. Starmer, said the results also reflected longer-term trends, including a breakdown of traditional class loyalties among voters, the increasing pull of nationalist politics and growing support for the centrist Liberal Democrats, the Greens and independent candidates.
“We have been seeing the fragmentation of society and that has flowed through to our politics,” said Ms. Ainsley, who now works in Britain for the Progressive Policy Institute, a Washington-based research institute. “There is multiparty voting now.”
The upshot is that both main parties are struggling as they find themselves competing not just with each other, but also with opponents to their political left and right.
That mood of public disenchantment gave an opening to smaller parties including the Liberal Democrats, who won 163 council seats, and the Greens, who gained 44. But the biggest beneficiary was Reform, whose supporters have been energized by Mr. Farage’s vigorous campaigning.
In an interview at a Reform U.K. rally in March, John McDermottroe, a party supporter, said many people in his region of Stockton-on-Tees, in northeastern England, felt that the Labour Party had “grown away from working people.”
As for Mr. Farage, “he is very charismatic, he communicates with people from every sector of life, he tells it as it is,” Mr. McDermottroe said.
The fragmentation Mr. Farage has unleashed on British politics was felt even in races Reform lost, including the mayoralty of a region known as the West of England.
Helen Godwin of Labour won that with just one-quarter of the vote, putting her only slightly ahead of Reform U.K., while even the fifth-placed party won 14 percent of the vote.
Fewer than one-third of eligible voters cast a ballot, the kind of low turnout that is common in local elections. But that meant Ms. Godwin was elected by just 7.5 percent of eligible voters, Gavin Barwell, a former chief of staff in Downing Street and member of the opposition Conservative Party, noted on social media, adding that there was a “collapse” of the two-party political system.
That may yet prove an exaggeration.
Because of a reorganization, the number of seats contested in Thursday’s local elections was the smallest since 1975, and voter turnout is always low in such races.
Britain’s next general election — when that proposition will be tested properly — does not have to be held until 2029, and previous challenges to two-party dominance have faded.
In the early 1980s the Social Democratic Party, founded by disenchanted moderates from the Labour Party, promised to “break the mold” of British politics. In alliance with another centrist party, it briefly exceeded 50 percent in an opinion poll. That proved a false dawn.
Yet with five parties now vying for votes in a system that suited two, British politics has become deeply unpredictable.
Born out of the trade union movement, Labour was once seen as the party of the working class, with its heartlands in the industrial north and middle of the nation. Traditionally, the Conservatives represented the wealthy and middle classes, with support concentrated predominantly in the south.
The loosening of those ties had already weakened the grip of the two main parties. In last year’s general election, the combined vote for Labour and the Conservatives fell below 60 percent for the first time since before 1922, and Labour’s landslide victory was achieved on just about 34 percent of the vote. In Scotland, the pro-independence Scottish National Party has reshaped politics.
Mr. Starmer now faces a conundrum: If Labour tacks right to appease Mr. Farage’s sympathizers, it risks losing support from its progressive base to the Liberal Democrats or the Greens.
Ms. Ainsley said Labour faces “an enormous challenge” in the context of a tight squeeze on government spending, but added that it must focus on delivering for voters still suffering from a jump in the cost of living.
The Conservatives face an even bigger threat from Reform, as well as their own challenge. The Tories need to recapture voters who have shifted to Mr. Farage without moving so far to the right that they drive more liberal Tories to the centrist Liberal Democrats.
Political scientists also say that a shift is underway that could transform the fortunes of Reform, taking what has been a protest party and turning it into a force that could make good on its ambition to replace the Conservatives as the main opposition party.
Britain’s parliamentary elections operate under a system known as “first past the post” in which the candidate who wins the most votes in each of 650 constituencies is elected. Until now that has typically disadvantaged smaller parties.
“When it was just the Lib Dems trying to break the Labour-Tory duopoly, a rough rule of thumb was that they, and their predecessor parties, needed at least 30 percent to overcome the biases inherent in first past the post,” wrote Peter Kellner, a polling expert.
With more parties in contention and no dominant force, the calculations are changing. “The tipping point for a party such as Reform is no longer 30 percent. It’s probably around 25 percent. That is where they stand in the polls,” he added.
Professor Ford said he agreed that something fundamental was shifting and that Reform was now “doing well enough for first past the post to cease being their enemy and to become their friend.”
After the latest election results, Professor Ford said, it is “a lot easier for Nigel Farage to say ‘We are the real party of opposition,’ and it’s harder for people to laugh when he says it.”