Boris Johnson is comfortably ahead in the polls but he also needs a good turnout from Tory supporters on Thursday.
Here, The Mail on Sunday reveals the 40 seats which Tory strategists hope to win to give the PM the majority he needs to deliver Brexit.
They include 20 won by the party in 2017, but which could fall due to tactical voting; and a further 20 which need to be seized from opponents. If you live in these seats, vote for Boris and stop Corbyn!
The 20 seats which must stay blue
The Tory Brexiteer is clinging on to a microscopic majority of 45 votes in a constituency where 70 per cent backed Remain in 2016.
Only 23 Tory voters would have to switch to the Lib Dems for him to lose.
Zac, son of the late Eurosceptic businessman playboy Jimmy Goldsmith, first won the seat in 2010, before losing it to the Lib Dems’ Sarah Olney when he quit and called a by-election over the proposed expansion of Heathrow.
He won it back from Ms Olney at the 2017 Election by that narrowest of margins, but she is hoping to keep up the game of Commons musical chairs by harnessing militant Remain sentiment.
Goldsmith is banking on local dread at the prospect of Corbyn being propped up in No 10 by the Lib Dems to get him back into Parliament.
By average income, the Cities Of London & Westminster is the second richest in the country after neighbouring Kensington, and has always been Tory.
But the majority was whittled down to a mere 3,148 in 2017 – in part due to the seat voting 71.9 per cent Remain.
Streatham MP Chuka Umunna has decided to stand here following his defection to the Liberal Democrats.
Incumbent Mark Field has stood down, so Westminster Council leader Nickie Aiken is taking his place as the Tory candidate.
Zac Goldsmith and Nickie Aiken are among the Conservative MPs that need to keep their seat at the upcoming General Election on December 12
The 20 seats which must turn blue