New data from pro-EU campaign Best for Britain shows that the Conservatives could win up to 366 seats unless the electorate gets out and votes tactically, say the group.
Their analysis of 39,476 voters using multilevel regression and post-stratification (MRP) found that this predicted majority depended on the Tories holding onto and gaining a “significant number of increasingly marginal seats” – meaning tactical voting will be decisive.
Their analysis is also the first MRP poll to adjust for the impact of the Brexit Party standing candidates down in 317 Conservative held seats and 40 more non-Conservative held seats, as well as the Unite to Remain alliance.
Without tactical voting, Labour, Lib Dems, SNP, Greens and Plaid Cymru would hold a combined 265 seats, predicts the group.
Labour would win 199 seats, Lib Dems would win 17 seats, SNP would win 44 seats, Plaid would win four seats and the Greens would win one seat, they say.
This scenario would see the Conservative Party gain a boost from 73% of Brexit Party voters who no longer have a Brexit Party candidate in their seat.
However, while the data currently predicts a Conservative majority, many of the seats they are anticipated to hold or win are vulnerable.
For instance the rise in Labour support, and fall in Conservative support, seen in the two recent polls (Kantar and ICM) could mean Labour gaining 24 seats, says the group.
If 4,000 or fewer pro-EU voters use their vote tactically in Best for Britain’s 57 target seats, they suggest that the Conservatives would be reduced to 309 seats – a dozen short of a majority.
At the beginning of the election campaign, Best for Britain’s polling found 131 seats where the margin of victory was less than 5,000 votes.
But now they say there are 165 seats in Great Britain which fall under this category.
This is around three times the number of seats Best for Britain’s data predicts that pro-EU parties would need in order to prevent a Johnson majority.
Best for Britain have therefore identified 57 target seats where they say the chances for tactical voting to succeed are highest.
These include seats such as the Cities of London & Westminster, Pudsey and Gordon.
According to outhe group’s data, it would take less than 4,000 tactical votes in these seats to prevent the Conservative Party winning.
Furthermore, in 27 of these seats it would take less than 2,000 tactical votes to prevent a Conservative victory, the group claims.
Nationally, Best for Britain estimates it could take as little as 117,314 pro-EU voters using their vote tactically to prevent a Tory majority – representing less than 1% of those who voted in 2017.
Best for Britain’s final update will be on December 9, three days before polling day.
The latest recommendations have been released to coincide with the first wave of postal votes landing on doorsteps.
Commenting, Best for Britain CEO Naomi Smith said: “Our data shows that tactical voting will be decisive at the upcoming election.
“Even with the Brexit Party collapse, there are still lots of seats in play for Remainers.
“This is crucial as it means they could be won by pro-EU parties if voters hold their nose and vote for the party with the best shot of beating the Tories.
“Having updated our recommendations just as the first wave of postal votes land on doorsteps, we’re confident that this election is up for grabs. We can stop Boris Johnson, and stop Brexit.”