The Conservatives have unveiled their candidate for the Eastleigh by-election as the party geared up for a brutal battle with its Liberal Democrat coalition partners.
Maria Hutchings will make a fresh bid to snatch the seat after ex-cabinet minister Chris Huhne, whom she narrowly failed to topple in 2010, quit after admitting dodging a speeding penalty.
Deputy Prime Minister Nick Clegg urged voters not to exact retribution for his former leadership rival's disgrace as the party formally moved the writ in the Commons for a February 28 poll.
The party, which holds a 3,864 majority, has not lost a seat in a by-election for more than 50 years but faces a bruising contest to hold on in the short campaign.
Tory chances have been boosted by UK Independence Party leader Nigel Farage's decision not to stand and David Cameron's party has indicated it will fight hard.
Sources said it was preparing a "big push" in the Hampshire town on Saturday when local Lib Dems are due to meet to select the party's own candidate.
Mrs Hutchings was thrust into the public limelight in 2005 when she challenged then prime minister Tony Blair during a TV debate over the proposed closure of a special school.
Mr Clegg earlier urged people not to take revenge on his party as he fired the starting gun on the campaign with a speech in central London.
"What has happened has happened with Chris Huhne and his guilty plea," he said.
"I think the choice for the people of Eastleigh in the by-election is what kind of an MP do they want to have now.
"I hope that it will be on that basis rather than in a mood or spirit of retribution that the debate will be conducted in Eastleigh."
He sought to draw a clear distinction with his Westminster coalition partners by highlighting the Lib Dem commitment to a 1% annual "mansion tax" on £2 million-plus properties to fund tax cuts for "hard-pressed families" - a proposal the Tories have consistently rejected.
Alternatively, he said, the Lib Dems would continue to press for the introduction of new council tax bands at the top end, again affecting properties worth more than £2 million.
"It's an open secret that our Conservative partners do not share our views on this. However, we will continue to make this argument, in this coalition and beyond.
"Our approach is simple: taxes on mansions, tax cuts for millions. An approach to tax that puts payslips before palaces."
Labour sources are hoping for a strong showing, but privately accept they have little chances of winning a seat where they came third in 2010 with fewer than 10% of the votes.
Tory sources pointed out that the party came second in 1994 and said any failure to make progress this time would mark a failure of Ed Miliband's "One Nation" project.
Labour deputy leader Harriet Harman said: "Nick Clegg can talk about his differences with the Tories as much as he likes - the issue is what he does.
"Nick Clegg's actions in backing a Tory-led Government tell a truth his speeches try to hide."
The local council is controlled by the Liberal Democrats