Labour’s number one target in this election is Southampton Itchen.
The party needs a tiny swing of just 0.03% to take the seat from the Conservatives.
Royston Smith is defending a majority of only 31.
There were two recounts at the 2017 election before the final result was declared.
The seat used to be one of Labour’s few toeholds on the south coast of England, with John Denham holding it for the party from 1992 continuously until 2015.
But in 2015 Mr Denham stood down, and his successor failed to get elected in the face of a swing to the Conservatives.
Royston Smith won it from Labour in 2015, only to see his majority almost obliterated two years later.
This year he faces the same Labour candidate as he did in 2017: Simon Letts.
Also standing in the constituency are candidates from the Liberal Democrats, Greens and Ukip.
Jeremy Corbyn visited Southampton on Thursday to launch Labour’s plans for the environment.
If his party fails to gain Southampton Itchen on December 12, a swing to the Conservatives might be under way across the region – which could mean Labour also fails to gain other targets in the south-east, including Hastings & Rye, Crawley and Worthing East & Shoreham.