The political map of the West Country could be set for a change in colour, as more than a third of Conservative voters in 2010 abandon the party – with almost half of them switching to Ukip.
Of the remainder, a fifth are aligning themselves with either the Liberal Democrats or Labour, and a third are not yet decided.
But a majority of the “defectors” (56 per cent) think David Cameron is the best of the three main party leaders and say their preferred outcome in 2015 would be a Conservative majority.
In a signal of the uphill struggle facing the party, the peer said it would need to win back all the lost Tory voters “plus practically everyone who is even prepared to think about doing so next time”.
But at present the number of new backers being attracted “are not enough to replace those going in the opposite direction”, he pointed out.
But of those who are switching to the Tories, more than two thirds are former Liberal Democrat voters - a statistic that could cause particular consternation in the West Country - where Tory candidates are often snapping at Liberal Democrat heels.
In Somerton and Frome, David Heath beat Annunziata Rees-Mogg by fewer than 2,000 votes; in Wells, just 800 votes gave Tessa Munt victory over David Heathcoat-Amory; and in Mid Dorset and Poole North, Annette Brooke held off a swing of 6.3 per cent from Liberal Democrats to the Tories as she won by just 269 votes.
The 2015 election will be a staunch test, with David Heath stepping down and Taunton's Jeremy Browne made to deny repeated suggestions that he would switch from the Liberal Democrats to the Tories following his sacking from the Cabinet in the autumn.
Lord Ashcroft said many voters in all camps gave at least a grudging recognition that the coalition had done well in dealing with the economy.
Mr Cameron and George Osborne were more trusted than Ed Miliband and Ed Balls to manage the economy in the country’s best interests by a margin of 57 per cent to 43 per cent.
But it would be “hard” to persuade people that they were feeling the benefits of improved growth rates in their own lives given that the Government had no scope for large giveaways.
In fact, a small majority 54 per cent said they expected no improvement or a slight worsening in the economy over the next one or two years – with 46 per cent anticipating a significant improvement.
In a more positive message for his party leadership, Lord Ashcroft said the polling found that “few swing voters see Ed Miliband and Labour as a credible alternative”.
The Opposition’s decision to focus on the cost of living had struck a significant chord with voters, with Labour leading by 51 per cent to 33 per cent on the issue.
They fell behind though when it came to introducing practical long-term policies to deal with it.
Lord Ashcroft said: “Drawing a contrast with Labour and highlighting progress on welfare, immigration and the macro economy, important though they are, will only take the Tories so far.
“It needs to be clearer what would be on offer under a new Conservative government. It is one thing to say don’t turn back, but we also need to know where we’re going.”
Ukip leader Nigel Farage said: “Given that they continue to ban new grammar schools, have opened our doors to Romania and Bulgaria and overseen a huge increase in our national debt, I hope and expect even more former Conservative voters back Ukip in the 2014 European Elections and General Election in 2015.
“They will be joining many of those who used to support Labour, the LibDems and who didn’t vote at all last time round in now getting behind Ukip as the true alternative to the establishment in British politics.”
The poll interviewed 8,053 adults online between November 4 and 10.