By Tim Castle - Analysis
LONDON (Reuters) - Voters, politicians and markets are being offered contrasting visions of the outcome of an imminent national election depending on which opinion polls they read.
One is a near consensus view that Britain is heading for its first hung parliament since 1974 with no single party in overall control; the other sees a comfortable victory for the Conservatives over Labour.
Most pollsters, including ComRes, ICM, Ipsos-MORI, Populus and YouGov, have reported a decline in the Conservative lead since mid-January from a double digit gap last year to between around 4 and 9 percent now.
By contrast, Angus Reid Public Opinion has consistently shown the Conservatives enjoying a double digit lead since it started surveying political opinion last year.
Uncertainty generated by the polls has buffeted sterling, with traders driving the currency down 4 cents after a particularly narrow YouGov poll earlier this month, before buying it back days later on an Angus Reid poll.
The pound has fallen 6 percent against the dollar since January, in line with the decline in the Conservative lead reported by the main polling firms.
The Conservatives' sterner approach to tackling the record 178 billion pound budget deficit has found favour in financial markets. The Conservatives want to get to work on the deficit this year, while Labour's deficit reduction measures would only kick in next year.
NOT ALWAYS ACCURATE
Polling companies have been measuring the political mood since the 1930s by interviewing a small but representative sample of the population and have a good track record of predicting election outcomes.
But they have suffered failures, miscalculating the outcomes of the 1948 U.S. presidential election, Britain's 1992 national vote and the first round of France's 2002 presidential race.
The current split in UK forecasting is caused by differing polling methodologies and creates a dilemma for anyone betting on the outcome -- which pollster, if any, should they trust?
The contest pitches an old guard of established research firms against the fresh kid on the block, Angus Reid -- part of Canadian research firm Vision Critical -- new to Britain but whose chief executive is well known in north America.
The Conservatives are seen needing at least a 10-point advantage if they are to be certain of a majority in parliament, because of an uneven distribution of the vote.
That has lead to a widely held view the election, expected on May 6, will have an inconclusive result, a prospect that unnerves markets almost more than any other.
Angus Reid has consistently put Labour's share of the vote around 5 percentage points below other polls, while finding comparable results for the Conservatives and the Liberal Democrat party.
Its research director Andy Morris said the firm remained "very confident we are calling this correctly" despite its forecasts lying outside the range of other researchers.
"If we look back at previous elections the pollsters tend to overestimate Labour," Morris said. "So being low on Labour is probably no bad thing."
FRINGE PARTIES
Around half its lower score for Labour comes from including a smaller proportion of people saying they voted for the party at the last election in 2005 than some of the other pollsters.
Labour's vote share also suffers from a higher proportion of Angus Reid's respondents -- all online, as are YouGov's -- saying they back fringe parties such as the eurosceptic UK Independence Party and the far-right British National Party.
Morris says the relative anonymity of the internet could be encouraging respondents to be more open about their preferences than if questioned by telephone canvassers.
The mainstream pollsters back their claim to be accurately recording the national mood by noting they all show broadly the same results despite operating their surveys in three quite different ways.
They have refined their methods over recent years to avoid a repeat of the disaster of the 1992 election when all polling firms forecast a Labour victory, only for Conservative Prime Minister John Major to win a surprise fourth term for his party.
"When things did go wrong in 1992, one of the causes of that was that everybody was polling in exactly the same way, and all making the same mistakes," said Roger Mortimore, head of political research at Ipsos-MORI.
"Unless we are all now making different mistakes and still coming to the same answer, we ought now to be rather more confident that we are getting it right."
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