Campaigners for David Rendel, the Liberal Democrat candidate, aim to ram home the 'tax and trust' issue to former Conservative voters in the erstwhile safe Home Counties Tory seat, forcefully reminding them of the Government's pre-general election message that it was opposition parties that could not be trusted not to put up taxes.
At the same time they will urge 'soft' Labour supporters to vote tactically for the Liberal Democrats, warning that a Tory victory would give a seal of approval to dearer fuel bills through the imposition of VAT, hitting pensioners and the poor, while justifying the continued tenure of Norman Lamont as Chancellor and giving a false boost of confidence to Mr Major.
The Liberal Democrats were still cautious yesterday as they and the Tories both renewed predictions of a close-run contest in spite of the NOP/Mail on Sunday's poll findings that 54 per cent of electors would vote for Mr Rendel and only 38 per cent for Julian Davidson, the Conservative.
Both sides pointed out that the sample - 752 adults across the part-urban, part-rural constituency - was relatively small, had been contacted by telephone, and that the 10 per cent 'don't know' and the 5 per cent 'won't say' figures were likely to have been underestimated. Against that is the by-election 'bandwagon' phenomenon of a poll galvanising undecided voters to back a perceived winner.
Private Tory scepticism was also to be contrasted with a direct appeal by Mr Davidson to prospective voters to back him. 'The one thing which will begin to erode confidence. . . is a result which suggests that people do not believe in the Government,' he said.
That was music to Liberal Democrat ears, as Mr Rendel declared the contest a referendum on the Government's economic failure. Matthew Taylor, the MP for Truro and Mr Rendel's campaign co-ordinator, highlighted NOP's finding that only 1 per cent were 'very satisfied' with the Government's performance since the election.
Mr Taylor said: 'We are not surprised by that - and this is in the heartlands of Conservative southern England. While we are glad the economy is picking up people clearly don't feel it's because of the Government or that the Government deserves any pat on the back.'
NOP's finding that only 5 per cent of voters intended to back Labour, a squeeze of 1 per cent since the general election, reflects a tacit admission last week by Peter Mandelson MP, campaign minder for Steve Billcliffe, the Labour candidate, that the party would help to mobilise the protest vote without benefiting from it.
That about-turn from its earlier professed stance - in effect repeated by Mr Mandelson yesterday - and the impending collapse of the Labour vote will reinforce calls, currently anathema to the leadership, that the two main opposition parties must direct resources to winnable seats if they are to oust the Tories in a general election.
Ladbrokes, the bookmaker, puts the Liberal Democrats at 3- 1 on favourites to win the by- election, while the Conservatives are 6-4 and Labour 1,000-1 outsiders. William Hill is offering 6-1 on on the Liberal Democrats, 100-30 against the Tories, with Labour at 200-1.