The Tories are on the brink of their first by-election victory over Labour in three decades as the Crewe and Nantwich battle reaches its climax.
With polls indicating another ballot box kicking for Gordon Brown, some believe the Conservatives could even end up with a comfortable majority of 7,000.
Anything approaching that figure would be seen as disastrous for the Prime Minister, and a sign that voters want to punish his party for the faltering economy and botched 10p tax rate abolition.
However, there was a glimmer of hope for Labour on Wednesday night when the Tories suffered their first real glitch of the campaign. Officials accidentally emailed a radio station with personal information about more than 8,000 key voters, including their names, addresses, telephone numbers and financial status.
Cabinet Office Minister Ed Miliband wrote to David Cameron urging him to issue an immediate apology to those whose security could have been compromised. The Daily Mirror also reported that the Information Commissioner would be launching a probe into the incident.
The row emerged as voters go to the polls after a bad-tempered struggle in Crewe and Nantwich.
Many in Labour have been concerned by the "class war" tone of its campaign. The party has sought to brand Conservative candidate Edward Timpson - a barrister whose family founded the Timpson shoe repair business - as a "Tory toff".
Meanwhile, all three main parties have poured resources into the constituency, which has been flooded with ministers and their opposite numbers over the past fortnight.
On Wednesday Mr Cameron accused the Prime Minister of hiding "in his bunker" by failing to visit Crewe and Nantwich during the contest, taunting him that he lacked the "courage" to lead from the front. But speaking in the Commons, Mr Brown rejected the claim that he was an electoral liability. "He knows that it is the tradition that Prime Ministers don't go to by-elections," he added.
Tamsin Dunwoody is defending Labour's 7,078 majority in Crewe and Nantwich. Her mother, Gwyneth Dunwoody, held the seat until her death last month. The Lib Dem candidate is Elizabeth Shenton.
