(Bloomberg) -- Keir Starmer becoming UK prime minister next week has long been accepted by Rishi Sunak’s team. But the Conservative campaign fears a heavy election defeat to Labour is morphing into a wipeout due to something all but impossible to counter: tactical voting for the Liberal Democrats.

Conservative strategists have privately conceded for months that the prevailing public mood is a desire to change government. The Tory view is that is less about enthusiasm for Labour and Starmer than it is about ousting Sunak’s party after 14 years dominated by political and economic turmoil.

Their concern now is that Sunak’s error-strewn campaign has compounded that feeling, and a record number of voters in seats with big Tory majorities are backing Ed Davey’s Liberal Democrats to get the Conservative MP out. 

Polling analysis by Electoral Calculus on Friday showed the Liberal Democrats, traditionally the third party of British politics, gaining more seats than the Tories and becoming the official opposition in Parliament. That would send shock waves through Westminster and pose an existential threat to the 300-year-old Conservative Party — though the Tories and Labour say it’s unlikely.

Tactical voting is not a new phenomenon in the UK. But officials on the Tory, Labour and Liberal Democrat campaigns all told Bloomberg they’ve seen evidence of large numbers of people in key Conservative-held districts using online tools to determine the best way to vote to oust their Tory MP. They said that was likely why the Liberal Democrat vote share has risen in Bloomberg’s polling composite to 11.3%, from around 9% at the start of the campaign.

In 234 out of the 650 House of Commons seats, as many as 40% of people intend to vote tactically for a party other than their first preference “to see the back of the Tories,” said Naomi Smith of the Best for Britain campaign group, which has carried out polling and set up a website to aid tactical voting.

Ipsos surveys show one in five voters plan to vote “in order to stop another party getting in, rather than for the party that best represents their views,” said the pollster’s research director Keiran Pedley. That is up from 14% ahead of the 2019 election, and almost twice as high as 2010, he said. 

“This behavior looks primarily motivated by anti-Tory sentiment,” Pedley said, noting that one in three Liberal Democrat voters and one in four Labour voters said they would be voting in that way. Tactical voting could partly explain the scale of a Labour victory, he said, but the overall win would still be down to issues like the economy, immigration and the National Health Service.

Conservative activists campaigning in traditional strongholds — rural, commuter areas around London and in southern England — report going hours not meeting anyone saying they’re planning to vote Tory. Seats like Henley and Thame, an affluent area in Oxfordshire known for an annual regatta that’s a high point of the social season, are projected by pollsters to fall to the Liberal Democrats.

That’s a prospect that would previously have been unthinkable. It’s in part due to local scandals involving sewage being pumped into the Thames river that flows through the district, as well as opposition to Brexit, but above all else it’s down to a general feeling of anger at Sunak and his party, the people said. Voters just want to punish the Tories, one candidate said.

In the Surrey commuter belt, for decades home to successful City of London types and where Chancellor of the Exchequer Jeremy Hunt told Bloomberg he’s within 1,500 votes of losing, the Liberal Democrats expect to win several seats. Davey will spend the final days of the campaign mostly in Tory-held seats in southwest England, and in the southeast. 

Conservative headquarters has told more than one Cabinet minister they will lose their seat to the Liberal Democrats and that campaign resources will be redirected to defend other safer areas, people familiar with the matter said. 

In many areas, the Liberal Democrat vote is one factor in the Tories potentially losing. Nigel Farage’s Reform UK party is also drawing Conservative voters. A key question in the coming days is whether Reform can maintain its momentum, after a series of revelations about racist comments by its supporters, as well as Farage’s controversial views on Russia and its war in Ukraine.

Meanwhile, Labour is relaxed about the Liberal Democrats potentially taking swathes of seats in southern England. Starmer’s party considers a best-case scenario will be winning more than 400 seats, which would translate to a majority comparable to Tony Blair’s landslide win in 1997.

Still, Labour officials also say that millions of voters remain undecided and that the scale of any victory is far from certain. Starmer will repeat an adapted slogan — “change will only happen if you vote for it” — to avoid voters staying at home on July 4 assuming the result is a foregone conclusion.

Even some Tories, while bemoaning the quality of Sunak’s performance since he called the election, privately praise the professionalism of the Labour campaign, which has yet to come seriously unstuck after a brief row about treatment of left-wing candidates in the opening week. 

Conservative officials said Labour effort’s was better organized, with message discipline they could only dream of. One Tory official said Labour’s attack operation, such as drawing attention to the gambling scandal engulfing Sunak’s party, blew his side’s out of the water. With five days to go, it wasn’t hard to see why the public appeared to want change, they said.

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