When he first became prime minister, Andy Burnham’s Conservative opponents labeled him a “people pleaser.”One hundred days on, polls have proved them right: Burnham has helped Labour record one of the biggest popularity boosts enjoyed by a party that has switched prime ministers outside of a general election in over 70 years.

The party’s share has increased to 28% in surveys of voter intention, up from about 19% just before Burnham’s predecessor Keir Starmer announced his resignation, according to Bloomberg’s composite poll, a rolling 14-day average using data from nine polling companies.

The trend vindicates the governing party’s decision to replace its leader just two years after a sweeping election victory, as well as Burnham’s conviction that he could sell the government’s vision to the country better while taking on polarizing issues, like the UK’s relationship with the European Union and the burgeoning cost of state pensions.

The improvement has come in broadly three stages: when Starmer announced his resignation, when Burnham became prime minister, and after the new leader’s speech to Labour’s conference last month, which he used to set out an ambitious policy platform.

The nine percentage-point jump is behind only the increase secured by Boris Johnson when he replaced Theresa May in 2019 and that enjoyed by Gordon Brown after replacing Tony Blair in 2007. That’s according to Bloomberg’s analysis of polling data compiled by Liberal Democrat peer and poll expert Mark Pack that stretches back to 1955, and is more than double the average boost recorded after mid-term changes of prime minister.

Under the UK’s first-past-the-post voting system, parties can capture large Commons majorities on a small proportion of ballots, like Starmer did in 2024 when Labour won almost two third of seats on a third of the votes.

But Burnham has repeatedly ruled out the temptation to renew his mandate by calling an early election. And there are plenty of reasons for him to remain cautious. The average bounce for a new premier peaks after roughly four months, according to the analysis, and turns negative within a year.

Even though Johnson won a large majority in the snap election he called months after becoming prime minister, he was out of office three years later, brought down by a succession of scandals. Brown enjoyed a similar bump to Burnham when taking over, only to lose power three years later in the election that followed the financial crisis.

For Burnham, the landscape could be radically different again by the time an election is called. The prime minister is less than halfway through the maximum parliamentary term and, for this stage of a parliament, it’s been one of the most changeable for public opinion on record.

Adding up quarter-by-quarter movements in support between parties, it’s been tied for the most volatile Parliament since 1955 alongside the 2017-19 parliament, which took place during the turmoil of Brexit negotiations.

With five parties consistently polling above 10%, it’s also the most fragmented: at one point the poll-leading party was averaging just 25%. Before 2015, a party had never led the polls with less than 33%.

Polls also show the Tories overtaking Reform UK to become the most popular right-wing party for the first time since January 2025, in what could be a tipping point in the battle to represent conservative voters.

Reform’s slide — to about 20% from 30% over the last 12 months — owes to campaign-finance scandals as well as the way they’ve been outflanked by insurgent far-right party Restore, according to Rob Ford, a professor of politics at the University of Manchester.

“These things always move more slowly than people who follow politics closely expect,” he said, adding that Nigel Farage’s party could slump further, depending on the outcome of a parliamentary investigation into his financial declarations.

A significant minority of Reform voters simply want a right-wing government and are willing to support whichever grouping is best-placed to deliver it, pollster Luke Tryl of More in Common told Bloomberg.

He estimates that as many as two-fifths of Reform’s current supporters — or 8% of all voters — would switch to the Conservatives if Kemi Badenoch’s party were leading in a closely-contested election against Labour. Those voters won’t move straight away since a ballot isn’t imminent, but could be decisive in a campaign, Ford added.

The Conservatives’ gradual increase in support, alongside Labour’s more dramatic boost, also means the two traditional parties command a majority of the public’s support for the first time in almost two years.

With Burnham and Badenoch offering contrasting ideological views on the size of the state, the country is shifting away from the “managerial politics” espoused by their predecessors Starmer and Rishi Sunak, who sought to appeal to voters on the basis of competent government.

Still, their combined 50% support is far behind the roughly 80% postwar average enjoyed by the two parties.