Conservative strategists, who appear to have written off the previously safe Tory seat, believe John Major has a good chance of holding on to office in a May general election.
While Mr Heseltine said in the Wirral village of Thornton Hough that the Tory majority in the election would be "60 and nudging up", party strategists said a "lesser win" would be enough - a hung parliament in which the Conservatives remained the largest party but without an overall majority.
In that event, one senior Conservative said Mr Major would seek to govern with the support of Ulster Unionist MPs, Labour would fall apart in a bout of acrimonious blood-letting, and Britain could well go into the 21st century with the Tories facing a newly created alliance of moderate Labour and the Liberal Democrats.
Forecasting an unexpected Tory win in the general election, as opposed to the drubbing expected by everyone for the Tories in Wirral South tomorrow, Mr Heseltine told The Independent: "You have made this mistake before.
"You are confusing the decision about who governs the country in a general election and the protest that people indulge in, in other circumstances, either with pollsters or by-elections, whatever it may be."
Mr Heseltine said at the start of the campaign that there was a by-election "culture" in which the voters kicked the Government party.
But he said yesterday that there was a totally different culture in general elections.
"People ask different questions in these two alternative circumstances. When people go to vote in a general election they know that the consequence of that vote is to elect for five years a government.
"They will see as they do now this country's economy in one of the most exciting prospects I can remember and when faced with a Labour Party that would risk that prosperity, they will not vote for the Labour Party."
The distinction between this week's by-election and the general election was being stressed heavily by senior Conservatives yesterday. They argued that they remained firmly in the running for victory in May's election contest.
It was argued that the polls were being misinformed, because being a Conservative was more unfashionable than it had been in 1992, and people were therefore reluctant to disclose their real voting intentions to the pollsters; a Labour victory would require an unprecedented swing, and Tony Blair would need to win more than 60 seats to overcome the Tory majority and the boundary-change hurdles, all at a time when the economic climate was "more favourable than it has ever been before".
In addition, one source said, Labour could lose seats in Scotland and the Liberal Democrats could also lose seats in Scotland and elsewhere.
The source said even if there was a "lesser win", with a hung parliament that left Mr Major in office, that would be enough, because the "golden boy lure" of Mr Blair would have been destroyed and a realignment of the left forced, which would wipe out the last vestiges of Labour's socialism.
Mr Major, it was said, would have defied the pundits by winning the election at all.
One confident Tory source made the point yesterday that after the last election, The Independent carried a cartoon showing Mr Major driving a fairground dodgem, with Labour and the Liberal Democrats standing to one side, asking when it would be their turn. The Prime Minister was telling them: "We're not playing turns anymore."Reuse content