While rejecting requests to publish canvassing returns, Tim Payne, the agent for David Rendel, the Liberal Democrat candidate, revealed that of the 23,000-24,000 voters canvassed so far - including 7,000 at the weekend, one in three had yet to make up their mind. The vast majority of these voted Tory in 1992.
The Liberal Democrats believe they have halved the Conservatives' 12,000-plus general election majority and that the gap will be closed with a late surge of Tory defectors.
Mr Payne said large numbers, as yet unspecified, were considering switching their vote. 'We are confident that a lot of these 'undecided' voters will come to us in the last few days,' he said, adding that the party's progress so far equalled that achieved at the halfway stage in the 1990 and 1991 by-elections in Eastbourne and Ribble Valley.
Those two contests, coinciding with the impending demise of Margaret Thatcher and the poll tax, saw swings of 20 and 24.7 per cent. Mr Rendel needs a 9.3 per cent swing to take Newbury.
Mr Payne said that 1,500 people had also taken the trouble to post coupons in support of the Liberal Democrats' petition against VAT on fuel. A petition urging the speedy go-ahead for a new district hospital had also attracted 1,000 signatures.
Until now, the Liberal Democrats have tended to resist any temptation to talk up potential victory. The earlier morning news conference seemed to show the party in jittery mood. Mr Rendel appeared cautious, saying there was 'a large number of people undecided, waiting to be convinced'.
But despite a slightly rocky atmosphere, Matthew Taylor, the campaign co-ordinator and the MP for Truro, said: 'We believe victory is in sight in this campaign. It is clear that the Conservatives believe they are under immediate threat.' Julian Davidson, the Tory candidate, retorted: 'They are on the ropes while the Conservatives are setting the agenda.'
Meanwhile, Labour made it clear that its objective was to increase the party's share of the vote - even if that meant splitting the protest vote and returning a Tory MP.
Robin Cook, Labour's trade and industry spokesman, said: 'If the Liberal Democrat wins it will be easy for the Government to write it up as something that can easily be reversed. If there is a thumping Labour vote in Newbury that will be much more difficult to write off.' The remarks confirmed continuing resistance to the notion that Labour should stand aside in seats it cannot win.
Chris Rennard, the Liberal Democrat director of campaigns, expected a turnout of about 75 per cent. 'I think there is a lot of apathy. A lot of the undecided voters are people who are fed up with all politicians.'