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Sex, lies and scandal — not the usual ingredients of a parliamentary special election in Britain.

But Thursday's contest for the southern English constituency of Eastleigh has been overshadowed by the torrid trials of the centrist Liberal Democrats, including the criminal conviction of a former Cabinet minister and allegations of sexual harassment against a senior party official.

The election was called to fill the seat vacated by ex-Energy Secretary Chris Huhne, who resigned earlier this month after admitting that, a decade ago, he had asked his wife to take a speeding ticket for him, even though he had been driving. He faces a possible jail term for perverting justice, and his high-flying political career is in ruins.

The Liberal Democrats' efforts to hang onto the seat have been hampered by accusations that former chief executive Chris Rennard inappropriately touched and propositioned several women in incidents dating back a decade.

Scotland Yard detectives have been asked to investigate, and at least one former party worker says she will make an official complaint against Rennard, who stepped down in 2009.

Lib Dem leader and Deputy Prime Minister Nick Clegg has been accused of failing to act after admitting he had heard stories about Rennard's behavior several years ago.

"There were some very serious mistakes and the women were not listened to and were let down," Clegg said Wednesday.

The troubles are the latest woes for Clegg's party, which became the junior partner in Britain's Conservative-led coalition government after the 2010 national election.

Since then the party's popularity has sagged as the economy flagged and the Lib Dems abandoned several key election promises — most controversially, a vow to abolish university tuition fees. The Lib Dems backed a government decision to triple them instead, a move that sparked violent student protests.

The party has been tarred further by the fall of Huhne, whose ex-wife, Vicky Pryce, is currently on trial for taking his speeding points and lying about it.

The other main parties may be enjoying the Liberal Democrats' discomfiture, but they face troubles of their own.

The Conservatives hope to take the seat from their coalition junior partners, but their candidate, Maria Hutchings, has made several gaffes, including being quoted as saying that state high schools were not good enough to help her bright son become a surgeon.

The Labour candidate, a well-known humorist, is under fire for remarking, in a 1998 book, that he felt a fleeting sense of disappointment that Margaret Thatcher had not been killed in a 1984 IRA bombing. Five people died in the attack on the Grand Hotel in Brighton.

Prime Minister David Cameron called John O'Farrell's comments "a complete disgrace."

O'Farrell defended himself on Twitter, posting: "I wrote an honest memoir and volunteered this fleeting bad thought from 1984 to illustrate how hatred can poison politics."

The big winner could be the small U.K. Independence Party, which seeks British withdrawal from the European Union and has no parliamentary seats. It is unlikely to win but hopes to come second.

"This is the campaign that has got momentum," said UKIP leader Nigel Farage.

Polls suggested a close race between the Conservatives and the Liberal Democrats. Results of the election are expected early Friday.

Clegg was asked Wednesday why voters should trust his party.

It was, he conceded, a "fair question" — before saying he hopes voters would judge the party on its record on the economy and other issues.

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Jill Lawless can be reached at http://Twitter.com/JillLawless