Nigel Farage believes efforts to discredit him and his party are failing - and the polls suggest he may well be right.
Almost one third of Britons think that Ukip is a racist party, according to a new ITV News/ComRes poll.
Conservative MP Patrick Mercer has been accused of breaking parliamentary rules by offering to provide a Commons pass for lobbyists.
UKIP Leader Nigel Farage will arrive in Swansea today as part of his UK wide tour in the run up to the European Elections.
Mr Farage is due hold a walkabout in the city centre and a rally at the Liberty Stadium in the evening.
Nigel Farage decided not to stand in the Newark by-election, as he knew he could not win, according to Conservative Cabinet minister Ken Clarke.
"I am not really surprised. Whatever else Nigel is, he is not an idiot and I don't think he'd have the faintest chance of winning in Newark," he told the BBC.
Earlier the Ukip leader said: "I don't have any links with the East Midlands, I would just look like an opportunist and I don't think that would work."
But he added: "We will fight the Newark by-election and fight it damned hard and get a good local candidate.
UKIP leader Nigel Farage has said he will not be standing in the Newark by-election because he does not want to "distract" from the party's European election campaign.
He told the BBC: "I don't want to do anything that deflects from the European election campaign, so I am not going to stand in this by-election.
"I want to focus the next three weeks on winning the European elections."
Mr Farage added he was predicting UKIP would cause an "earthquake in British politics".
UKIP leader Nigel Farage has told the BBC he will not be standing in the Newark by-election, sparked by disgraced former Tory minister Patrick Mercer's decision to quit over a cash-for-questions scandal.
Nigel Farage has said his lack of connections with the local area may mean he chooses not to run in Newark.
A by-election in the constituency was triggered after the resignation of Tory MP Patrick Mercer over a cash-for-questions scandal.
The Ukip leader told the BBC:
I know that winning one seat in Westminster would completely transform the landscape for us as a party in terms of our prospects.
What I've got to work out is, is it the right seat for me. And I just...my reservation in my mind is I haven't particularly got connections with the local area.
Ukip leader Nigel Farage hinted that he may stand for election as an MP in the next few weeks.
A seat will become available after a former Conservative, Patrick Mercer, announced he is stepping down.
ITV News Political Correspondent Romilly Weeks reports.
Nigel Farage has told ITV News he is "going to think very hard" about whether to stand as Ukip's candidate in the Newark by-election triggered by Patrick Mercer's resignation as an MP.
When asked whether he would run in the poll, Farage said: "I'm going to think about it. We're very keen to get our first MP in Westminster because once that happens, the damn will burst."
The by-election is expected to take place in the summer, soon after next month's European elections.
Patrick Mercer won more than 50 percent of the vote in Newark - a majority of 16,000 - when he stood as the Tory MP in the 2010 general election.
The Ukip candidate, Reverend Major Tom Irvine, won just 3.8 percent of the vote. However, Nigel Farage would be expected to fare better if he were to run as the party's candidate in a by-election.
Ukip has never won a seat in the House of Commons.
Ukip plan to run a "serious and impressive candidate" in the Newark by-election triggered by Patrick Mercer's resignation as an MP, a party source has said.
"If there is a by-election very soon after the European elections it would be quite a big deal, particularly if Ukip has given the Tories a bloody nose, we would want to run a serious and impressive candidate," the source said.
The by-election could provide an opportunity for Ukip leader Nigel Farage to contest a Westminster seat to capitalise on his party's popularity.
Mercer held Newark with a Conservative majority of 16,152 in 2010, but the by-election will cause a headache for David Cameron - particularly if Farage decides to stand.