The polls have now closed in the Rochester and Strood by-election.
Mark Reckless, who defected from the Conservatives to Ukip, is the favourite to retain his seat, where he stood down when he changed parties.
Should Reckless win the seat, Ukip will have their second elected MP.
Ukip will land a second voice in Parliament next month according to a new poll that puts the party a commanding 13 points ahead of the Conservatives in the run up to the Rochester and Strood by-election.
A ComRes study tips the Eurosceptics to get 43% of the vote, well ahead of the Conservatives on 30%, as Tory defector Mark Reckless bids to regain his former seat for Nigel Farage's party.
Labour trailed in third on 21%, while the Liberal Democrats were way back on 3% alongside the Greens ahead of the November 20 poll.
ComRes interviewed 1,500 adults in the north Kent constituency by telephone between October 17-21.
Conservative Party Chairman Grant Shapps told the party conference defecting Mark Reckless has "abused" their trust.
"Today your trust has been abused, you have been cheated, but worse, the people of Rochester and have been cast aside," Shapps said.
Conservative defector Mark Reckless has rejected charges he acted in bad faith in leaving the party for Ukip.
The MP for Rochester and Strood insisted he was "trying to do the right thing by his constituents" and accused David Cameron of breaking his election promises.
"I made a lot of promises to my constituents and I want to keep those promises on immigration, on the deficit, on political reform. The Prime Minister isn't keeping those promises, I want to do so and that's why I'm moving to Ukip," he told BBC's Sunday Politics.
"We made all these promises in 2010 as Conservatives and they have been broken."
Conservative MP Mark Reckless was one of 43 MPs to vote against today's motion for British air strikes in Iraq.
The right-wing politician explains his position in this tweet:
Tory MP Mark Reckless accompanied Keith Vaz at Luton Airport, claiming he was concerned that large numbers of Romanians and Bulgarians may come to the UK.
Mark Reckless MP has said around 40 MPs had backed the motion and there were "many others" who would vote for it.
Speaking in the BBC Radio 4 Today programme, he urged MPs to "reflect the interests of their constituents" in today's debate.
He said: "I think there are about 40 names on the order paper, all those Conservatives MPs have supported, signed my motion, and I know of many others who are going to vote for it and many, many more who would like to vote for it."