David Cameron has attempted to fight back against resurgent Liberal Democrats with a personal address to voters in a Conservative party election broadcast.
In an apparent indication of concern among Tory top brass at polls which have seen them challenged - and even pushed into second place - by Nick Clegg's party, Mr Cameron scrapped a film attacking Labour.
Instead, he recorded a new statement warning a hung Parliament would result in indecision and could leave Britain "stuck" with Gordon Brown.
The Prime Minister himself recognised that Mr Clegg was enjoying a "political honeymoon" sparked by his widely-praised performance in last week's TV debate - but he predicted it would be short-lived.
Both Labour and the Conservatives sought to pick holes in Lib Dem policy, with Mr Brown denouncing plans to cut back on child tax credits and not to replace the Trident nuclear deterrent, while Mr Cameron attacked the party's policies on immigration and tax.
But Mr Clegg said it was only to be expected that the two parties which have dominated British politics would "lash out" as soon as voters showed they were ready to choose "something different" in the May 6 General Election.
"The General Election campaign is starting to come to life for the simple reason that a growing number of people are starting - and it is only a start - to believe, starting to hope, that we can do something different this time," said Mr Clegg on a campaign visit to Cardiff.
"That the old tired choices that they have been given by the old parties of the past no longer need to govern the way in which we run politics in the future - I think that is tremendously exciting."
A YouGov poll for The Sun put the Lib Dems on 33% (up three points since a similar survey published on Saturday), ahead of the Tories on 32% (down one), with Labour trailing on 26% (down two). And an ICM survey for The Guardian saw Mr Clegg's party soar by 10 points over the week to 30%, three behind the Tories on 33% (down four) but ahead of Labour on 28% (down three).
They were the latest in a string of polls suggesting last Thursday's debate has turned the 2010 election into a three-horse race.