Whether the seat will be held by Labour or won back by the Conservatives is set to be decided by just 415 votes, researchers claim.
As a result, voters in the constituency "will wield 27 times more power" than those in the rest of the UK.
And now even the bookies are offering exactly the same odds for a Labour or Tory victory.
Labour candidate Rosie Duffield says the findings show the battle for Canterbury is "on an absolute knife edge" and that this is "the most important election in a generation".
Tory rival Anna Firth agrees the seat is one of the constituencies that will decide the election, which is "without doubt the most important in my lifetime".
The analysis has been published by the Vote for a Final Say campaign, a pro-Remain group.
Their work combines data from three MRP (multilevel regression and post-stratification) models, including those released last week by YouGov and Best for Britain, as well as work done by second referendum campaigners.
It predicts Canterbury will be the tightest race in the south east, and the sixth closest in the UK.
The campaign group has published a "Voter Power Index", which claims city residents will have 26.92 times more influence on the national result than those in other seats.
Ms Duffield said: "This is the most important election in a generation, and just a few hundred votes in constituencies like Canterbury, which are on an absolute knife edge, have the power to stop Boris Johnson in his tracks.
"Johnson spells danger for our country; his hard Brexit plans will hurt those who can least afford it, coming hard on the heels of a decade of Tory austerity which has already decimated our public services.
"We can and we must stop Boris Johnson, and voters in Canterbury have more power than most to do so."
But Ms Firth says voters are "far more terrified of Jeremy Corbyn running the country then they are of Brexit".
She added: "The real nightmare is waking up on Friday morning to Jeremy Corbyn and John McDonnell in Downing Street, supported by parties like the Scottish National Party.
"This would be an absolute disaster for our country, returning us to uncertainty, more referendums and a financial program that will destroy years of hard work.
"Only the Conservatives are promising to move the country on, allowing me to focus on important issues like fighting for a new hospital, addressing the significant infrastructure issues in the constituency and making sure that we receive our fair share of new police. We must seize this opportunity while we can.”
YouGov's MRP model also predicts Ms Duffield will narrowly hold on in Canterbury - her party's only seat in the county. This poll uses the same method that correctly predicted that she would overturn Tory Julian Brazier's 9,798 majority in 2017.
She won by just 187 - and YouGov believes Canterbury will once again be by far the most marginal seat in Kent.
The pollster predicts Ms Duffield is set to win 47% of the vote, ahead of Conservative rival Anna Firth on 43%. Lib Dem Claire Malcolmson is on 8% and independent Michael Gould on 2%.
But both Labour and the Tories admit there is still everything to play for in the constituency.
The YouGov model predicts Ms Duffield could receive anything between 39% and 54% of the vote. Ms Firth could receive between 36% and 51%.
Bookies Betfair are for the first time offering exactly the same odds for a Tory or Labour win in the constituency. Ms Duffield and Ms Firth are both at 5/6.
At the start of the campaign, the Tories were at 1/2 and Labour at 7/4. The Lib Dems have gone from 10/1 to 50/1.
The Final Say campaign hopes its findings will "focus efforts to mobilise high turnouts" and boost tactical voting by those opposed to Brexit.
They predicted Cheadle, in Greater Manchester, will be the country's closest race, decided by a margin of just 116.