Finchley and Golders Green, which Liberal Democrat leader Jo Swinson visited on Wednesday, is a constituency where a two-horse race has unexpectedly become a three-way fight.
The north London seat has always been one of Labour’s top targets.
The party needs a 1.6% swing to take it from the Conservatives, and at the 2017 election Labour managed to cut the majority of Tory Mike Freer from 5,662 to 1,657.
It ranks at number 20 on a list of Conservative seats most vulnerable to Labour.
But Finchley and Golders Green is now being eyed as a possible gain by the Liberal Democrats.
Their candidate is Luciana Berger: former Labour MP for Liverpool Wavertree, who switched to the Independent Group for Change in early 2019, before then joining the Lib Dems.
The Liberal Democrats came a distant third in the 2017 election, winning just 7% of the vote far behind the Conservatives (47%) and Labour (44%).
On these figures, it would need a swing of 20.2% for the Lib Dems to win the seat from the Tories.
The party believes it has a chance, however.
The local authority area in which the constituency is located, Barnet, voted 62.2% Remain in the 2016 EU referendum – the 30th highest Remain vote in the UK.
If the Lib Dems can attract the support of a large number of Remain-leaning voters, the party might jump from third to first place on polling day next month – particularly if those voters include a large quantity of former Labour and Conservative supporters.
An opinion poll carried out in the constituency in early October by the polling company Survation found the Lib Dems on 41%, the Conservatives on 29% and Labour on 25% – although the sample size (400) was small.
With three parties in contention in Finchley and Golders Green, the battle to win will be fierce – and the result could come down to a mere a handful of votes separating all the main candidates.