Thats a really curious dangler - in both ways.
Just imagine if say the left leaning Daily Mirror broke that piece of scandal, then I would imagine it would completely overshadow the election.
I am sure the very sharp New Labour team would have roasted such apparent lying. Norma Major might be temporarily seen as a martyr.
On election day, we would see even more Tory voters not turn up to cast their ballot.
Resulting in even more Tory seats vanishing. Perhaps a rump down to 150 with Labour taking a few, but more likely the Liberal Democrats winning the majority of the freshly lost seats.
To be truthful I doubt it would have made any difference really. Bar that it means the Conservatives will find it very hard to win an election for a generation.
If applied to today, I would suggest Brown might have called an election in 2007, with the confidence that the swing needed for a Cameron govt would be impossible to reach. Literally needing a doubling of their seats.