Voters in Thirsk and Malton face a wait to decide who will be their new MP after the Ukip candidate died.
The parliamentary election is to be delayed until May 27 to allow the party time to find a replacement for John Boakes.
Janet Waggott, Acting Returning Officer for Ryedale District Council, said: "It is with regret that we have been informed that John Boakes, the candidate for the UK Independence Party has died.
"The effect of the death of a candidate on the forthcoming UK Parliamentary Election is that the election in the Thirsk and Malton Constituency must be stopped and re-run. The revised date will be May 27 2010."
Only Ukip will be allowed to select a new candidate, she added.
Thirsk and Malton is a new constituency, but is notionally a safe seat for the Tories. Anne McIntosh, who was previously MP for Vale of York, is standing for the Conservatives.
It is rare for an election to be delayed in this way.
Voters in Staffordshire South had to wait seven weeks after the General Election in 2005 to settle who their MP should be after the death of the Liberal Democrat candidate.
But at the time it was reported to be the first contest to be put back in this way for more than 50 years.
Tory Sir Patrick Cormack held on to the seat on that occasion but called for the Electoral Commission to look into the delay.
Mr Boakes, who was in his 60s, is believed to have suffered a heart attack.
Ukip leader Lord Pearson said: "This is clearly very sad news, and our thoughts are with John's family.
"He was very dedicated to his country, and will be greatly missed by all his friends in Ukip."