Richmond Park and North Kingston residents are more upset about the UK's decision to split from the EU rather than the government's backing of a third runway at Heathrow airport, according to Sarah Olney.
The Liberal Democrat hopeful for the West London seat told IBTimes UK she would join her party's MPs in voting down Article 50, the official mechanism to break from Brussels, if she is elected to the House of Commons on 1 December 2016.
"We started our campaign talking about Heathrow, but what was coming to us very clearly from the doorsteps was what people were very much more upset about was Brexit," Olney said.
"That's why the election is becoming about Brexit rather than Heathrow."
The Liberal Democrats want to hold a second ballot on the terms of the UK's exit from the EU amid fears of a so-called 'hard Brexit', which would leave the UK left with severely reduced access to the bloc's single-market.
"We voted for a departure, not a destination," Olney said.
The by-election was triggered after former Conservative MP Zac Goldsmith quit the Commons in reaction to the government's decision to back the expansion of Heathrow.
The environmentalist is now standing as an independent.
Olney and Goldsmith both oppose a third runway at the West London site, but the pro-EU Liberal Democrats are hoping to exploit Goldsmith's Eurosceptic leanings after 69% of Richmond-upon-Thames residents voted Remain in this summer's EU referendum.
Olney may have the advantage on the EU issue, but Goldsmith, a former Mayor of London candidate, has a bigger local profile and more connections in the Commons, first being elected to parliament in 2010.
How would Olney, a 39-year-old accountant, be a better advocate for Richmond Park? "The trouble is that [Goldsmith] has been ineffective at stopping Heathrow expansion, and that's what's triggered the by-election.
"The one thing which might make Theresa May change her mind is if Richmond Park returned a Liberal Democrat MP instead of a so-called independent."
"There'll just be one of him, I'll be one of nine Liberal Democrats and 105 Liberal Democrat peers.
"A vote for him is effectively just a vote for the status quo, whereas a vote for me will send a very clear message to Theresa May."
The election result is expected to be tight after the Liberal Democrats were able to secure more than 30% of the vote, a second place and reduce the Conservatives' majority by around 20,000 at the Witney and West Oxfordshire by-election in October.
Ukip and the Greens, with the prospect of close race in mind, have decided not to contest the election, with the Eurosceptics backing Goldsmith and the left-wingers endorsing Olney.
Labour, despite splits in their own ranks over the airport expansion issue, have selected transport expert Christian Wolmar to fight the seat.
The party secured more than 12% of the vote in Richmond Park in the 2015 General Election. Is Olney worried that Labour could undermine her chances of unseating Goldsmith?
"It's up to Labour whether they stand or not, we certainly were not pressing for them to stand down. As far as I'm concerned, the more choice for the voters the better," she said.
A BMG Research poll of 543 people in Richmond Park found that 56% (-2) of voters backed Goldsmith, while 29% (+10) supported Sarah Olney.