Voters in the Irish Republic go to the polls on Thursday night to elect the country’s next president after a campaign of unprecedented political thrills and spills.

The main feature has been the heated questions about the IRA past of Sinn Fein’s Martin McGuinness, who has faced often hostile interrogation.

The seven candidates are a colourful cast of characters who include a former winner of the Eurovision song contest, an openly gay academic and one of the dragons from the Dublin version of Dragons’ Den.

The campaign has featured potentially embarrassing media revelations dwelling on the pasts of some of the candidates, with an unusual amount of mud-slinging concerning family, financial and sexual matters. Various threats about libel actions have been made.

This is extraordinary for Irish presidential elections, which are normally reasonably sedate affairs.

Last week’s drama came from the husband of Rosemary Scallon who, as Dana, won the Eurovision song contest in 1970. Damien Scallon claimed a tyre blow-out on his wife’s campaign car was caused by damage inflicted in an attempt to “injure or murder us”.

Police are investigating the incident, although tyre experts have said the damage was consistent with the vehicle being driven after getting a puncture.

The winner of the contest will have a hard act to follow: the outgoing Mary McAleese is regarded as an outstanding president.

Traditional politics has been shattered by upheavals sparked by the Irish economic nosedive, which brought about the near-collapse of the once mighty Fianna Fail. Its standing is now so low that it decided not to field a candidate.

This created a gap for Sinn Fein, which dispatched Martin McGuinness south of the border, causing a stir early in the campaign because many in the south found it difficult to come to terms with the idea of a former IRA leader serving in such a symbolically charged office as head of the Irish state.

Dublin commentators spoke out strenuously against this prospect, and there was widespread scepticism about his assertion that he had not been a member of the IRA since 1974.

One dramatic moment came when McGuinness was confronted, in front of television cameras, by the son of an Irish soldier shot dead by the IRA.

David Kelly demanded of him: “I believe you know the names of the killers of my father and I want you to tell me who they are.” When the Sinn Fein leader denied he knew the names, Kelly called him a liar.

McGuinness has been campaigning on his record as a peacemaker in the north and as an anti-establishment candidate who will stand up for those in economic difficulties. But he has lost ground, slipping from 17 to 11 per cent in opinion polls. Dublin bookies now rate him as a 25-1 outsider in what is being seen as a two-horse race.

Out in front is Michael D Higgins, an Irish Labour Party veteran with a long-standing interest in culture and international human rights issues. He is being pressed hard by the entrepreneur Sean Gallagher who, though involved only on the fringes of politics, became a familiar face through his appearances on Dragons’ Den.

Gallagher has risen spectacularly in the polls partly because of a dynamic campaign and partly because of his emphasis on business expansion and job creation. This struck a chord in a country hit hard by cuts and high unemployment.