Sleaford by-election candidates chosen by main parties
Lincolnshire county councillor Victoria Ayling has been chosen to contest the Sleaford and North Hykeham by-election for UKIP.
She joins Tory consultant paediatrician Caroline Johnson, who contested the Scunthorpe seat in 2010, coming second to Labour.
Labour selected its candidate - trade unionist and refuse driver Jim Clarke - on Wednesday.
Ross Pepper will be contesting the by-election for the Liberal Democrats.
Conservative MP Stephen Phillips resigned last week, citing "irreconcilable policy differences" with the government.
The barrister and part-time judge had complained that the government was "lurching to the right" and had criticised its attempt to trigger Article 50, beginning the formal process for the UK to leave the EU, without a vote by MPs.
The High Court has since ruled that the government must consult MPs - although ministers are appealing against the decision to the Supreme Court.
Lincolnshire voters were among the most Eurosceptic in the UK, with more than 75% of voters in Boston voting to leave.
This could benefit UKIP's Ms Ayling, who said she was "honoured" to be selected, and that as a local councillor she understands "the issues facing Lincolnshire."
Conservative Dr Johnson said she was delighted to be selected, adding: "I am the only person who can support the prime minister and the government to deliver Brexit. I am completely behind the government's plans for Brexit and to deliver on the decision made by the British people."
Mr Clarke, a trade unionist and former postman, said he was honoured to fight the seat for Labour and would stand up for locals in parliament.
"It is not right that in 2016 working people here in Sleaford and North Hykeham are having to choose between heating and eating."
He accused the government of having "no plan for Brexit" and pledged to "hold the government to account on ensuring the best deal for Britain, which protects our local jobs".
Local councillor Mark Suffield is standing as an independent while Peter Hill is standing for the Monster Raving Loony Party.