While the Liberal Democrats remain most commentators' favourite to snatch victory, there is now a big question over what will cut more ice: optimistic signs of recovery and falling job losses or attacks on the Government's past performance.
After the first week's campaign, moreover, it cannot be claimed that Julian Davidson, the Tory candidate, is a complete pushover - despite the initial derision he attracted as a gauche personification of lobby- fodder, and the widescale surprise that the local party should have selected him at all.
True, Mr Davidson wobbled at the daily news conferences as he was repeatedly thrown on to the defensive over VAT on fuel, one of the Liberal Democrats' prime weapons. His survival of that and other potentially embarrassing moments was due largely to the assiduous stage- management skills of his campaign minder, Gerry Malone, deputy party chairman and the MP for Winchester. But Mr Davidson's gamble of 'talking up' Newbury and his 'green branches' of economic recovery may have paid off, for the moment anyway.
Fast-talking and with an alertness belied by his bulky frame, he is adept at trotting out strings of loyalties to the Prime Minister. But he has a few ideas of his own, revealing himself for example as slightly to the left of Mr Major on Europe. A reformed exchange rate mechanism appears to hold no lasting terrors, provided central banks hold sufficient funds to protect banded currencies from speculative attacks. On education, he is also bold enough to accept that the implementation of testing has been a mess.
Mr Davidson, who at 30 would be one of Westminster's youngest MPs, was a Young Conservative in Kent while at Gravesend grammar school. After Durham University, he spent two years working on a Conservative campaign that won back Somerset County Council from the Liberal Democrats.
In the meantime, he built up a design company which printed stationery for local firms. After it folded in 1990, he concentrated on his political work as a Somerset county councillor.
Steve Billcliffe, a known local 'Labour man' and the party's conscientious by-election candidate, last week cheerfully predicted he might achieve 12 per cent of the vote. But David Rendel, the Liberal Democrat, is the prime vehicle for protest.
He is a management consultant turned full-time local politician as chairman of Newbury District Council's recreation committee. Married to Sue Rendel, a Newbury GP, he has a strong reputation locally for 'getting things done'.
Armed with copious local knowledge, he is adept at unpicking the surface benefits of Tory by-election sweeteners such as the go-ahead for the A34 Newbury bypass, and at analysing the detail of pressing local concerns such as the need for a new district hospital and environment arguments against the expansion of gravel-extraction operations.
On the doorstep and in the news conference he comes across as genuine if slightly patrician. At 44, he already has the air of a Liberal elder statesman, and is seen as both intelligent (a scholarship at Eton followed by Magdalen, Oxford) and trustworthy.
There is, however, no overwhelming sense of an impending by-election upset like Eastbourne or Ribble Valley. Despite the fact that many Tories said last week they intended switching their votes, by polling day it could be different story.