The polls have opened in three by-elections where defeats would heighten Conservative fears that Rishi Sunak will struggle to lead them to another majority.
The British prime minister told his backbench MPs on the eve of the polls that they face a “tough battle” in what were seen as safe seats for his party.
He told them that governing parties rarely win by-elections but urged the MPs to unite in the face of any defeat as he pledged to “throw everything” at winning the next general election.
Labour hopes to snatch Uxbridge and South Ruislip, which was Boris Johnson’s seat until he quit, and Selby and Ainsty – vacated by his ally Nigel Adams’ resignation.
The Liberal Democrats are eying victory in the contest in Somerton and Frome that was triggered by David Warburton quitting after admitting cocaine use amid allegations of sexual harassment.
Losses for the Tories in all of them would be the first time in 55 years that a government has been defeated in three by-elections on the same day.
On Wednesday evening, Mr Sunak was understood to have told his MPs: “In the coming months, I am going to set out more of what I would do if I had a full term.
“I was recently described as a full spectrum modern Conservative and you are going to see that in the programme I lay out.”
Mr Sunak pledged to show the public “who is really on their side”, adding: “And that is what will propel us to victory.”
He was conscious of the battle he will face if voters roundly reject the Tory candidates, but urged MPs to unite ahead of a general election expected next year.
“When we come back in September we have a choice to make, all of us. Do we come together and throw everything at winning the next election or not? I’ve made my choice, I’m all in with you to win,” Mr Sunak told the meeting.
“I promise you we can do this but we can only do it together as one team.”
Tory backbencher Jonathan Gullis told reporters outside the meeting that the problem is “apathetic Conservative voters” rather than the public’s support for Labour leader Keir Starmer.
He said Mr Sunak told them “what we already know, which is it’s going to be a tough battle” in the by-elections.
Tory MPs at the meeting said he did not address suggestions that he could spring a Cabinet reshuffle on Friday in an attempt to reset his premiership.
During a visit to Warwickshire, Mr Sunak told reporters asking whether he would shake up his top team that “you would never expect me to comment on things like that” – in what was clearly not a denial.
He welcomed a fall in the rate of inflation as proof his government’s plans were working.
Mr Sunak’s press secretary acknowledged it would be tough for the Tories to hold the three seats on Thursday.
She said: “By-elections, for incumbent governments, are very difficult, that is the nature of them.
“The election that the Conservative Party is most focused on is the general election.”
Mr Johnson held London’s Uxbridge constituency with a 7,000 majority when he was prime minister at the last general election in 2019.
Mr Adams secured North Yorkshire’s Selby and Ainsty with a 20,000 majority that night, a similar margin to Mr Warburton’s victory in his Somerset seat.
Lib Dem leader Ed Davey said: “Today voters across Somerton and Frome have a chance to send a clear message to the Conservatives that they have failed our country on the NHS, the cost-of-living crisis and protecting our rural communities.
“If the Liberal Democrats succeed in overturning this massive 19,000 Conservative majority, it will show voters in Somerset are fed up with being taken for granted by Rishi Sunak and his failing government.”
Mr Starmer’s spokesman downplayed Labour’s chances, saying Uxbridge was not won even during the 1997 landslide victory and Selby would require the party’s best by-election result since the Second World War.
