Earlier, elections guru Lord Hayward described Labour as being in a “mess” over the seat. He added: “It’s having real difficulties and the prospects for the Tories therefore are quite good.”
A former Tory minister said the situation was looking “increasingly optimistic” earlier this week.
Conservative Party co-chair Amanda Milling told the Standard last week it was a “much tougher” election than Hartlepool, adding: “I think we also have to remember that we are 11 years into government, governing parties don’t win by elections. Hartlepool bucked that trend.”
A poll carried out by YouGov for Sky found that four in ten Labour members believe Starmer should resign if he loses the by-election.
Seven in ten thought Andy Burnham, the mayor of Greater Manchester, would be a better leader.
Burnham, who lost the 2010 and 2015 leadership contests, told the New Statesman: “If there was a moment where that was right, then I’ve indicated that I would be prepared to go back.”
Boris Johnson visited the seat on Monday saying their candidate Ryan Stephenson had a “fantastic plan” to secure more jobs and get more police on the streets.
The by-election was triggered by the resignation of Labour’s Tracy Brabin after her election as West Yorkshire metro mayor.