The Conservatives and Liberal Democrats are to fight each other in the delayed Thirsk and Malton election despite the parties' new Westminster coalition.
Prime Minister David Cameron and his deputy Nick Clegg said they would still oppose each other in elections.
The North Yorkshire seat was the only constituency where there was no poll last week because of the death of the UKIP candidate during the campaign.
Voting will now take place on Thursday 27 May.
Conservative candidate Anne McIntosh was previously MP for the Vale of York seat, which disappeared after recent boundary changes.
She secured a majority of more than 13,000 in the 2005 general election in her old seat.
Parts of this seat form a section of the new Thirsk and Malton constituency, which covers a large area of rural North Yorkshire.
Lib Dem candidate Howard Keal, a Ryedale borough councillor from Norton, said: "It's a full-on fight, there's no question about it.
"I never expected anything else than we would fight the by-election. It was never in any shadow of a doubt.
"I hope people in our constituency will seize the opportunity we have been given to upset the apple cart."
'Very warm response'
Ms McIntosh said: "I have always maintained that every vote counts in this election and I think people's individual votes count more in this election than any other.
"I am obviously looking to get the maximum support for the Conservatives, for myself as a local candidate... but also now we will have the Conservatives in a majority partnership in a coalition government.
"Interestingly going round yesterday [Tuesday] we got a very warm response in Filey.
"We seem to be getting one or two Liberal Democrat switchers to the Conservatives, which was obviously very welcome.
Labour's candidate Jonathan Roberts said: "I will be fighting for every vote for Labour in this election and to make sure as many people as possible vote in the general election in Thirsk and Malton.
"I hope that people will support me as the candidate who will fight for fairness and will be hard working, open and transparent."
Meanwhile, UKIP named its new candidate for the Thirsk and Malton seat as Toby Horton, a former aide to the new foreign secretary William Hague.
Mr Horton said: "It is the first judgement of the new government and every vote will count and they have a real chance for the first time in generations to make their votes have an impact on the national stage."
He is standing following the death last month of UKIP's previous candidate John Boakes.
• The candidates standing in Thirsk and Malton are: Liberal: John Clark; UK Independence Party: Toby Horton; Liberal Democrat: Howard Keal; Conservative: Ann McIntosh; Labour: Jonathan Roberts.