Ed Miliband and Nicola Sturgeon are "at the altar, and preparing to sign the register" on a post-election deal, according to Scottish Conservative leader Ruth Davidson.
Sturgeon made the Labour leader an offer to join forces to help him become Prime Minister during the TV debates.
But David Cameron has warned there would be more borrowing and higher taxes if Miliband goes ahead with the deal.
People watching last night's "challengers' debate" were most impressed by Ed Miliband and Nigel Farage, the ITV News/YouGov daily poll suggests.
Miliband and Farage topped the table with 15% each, with the SNP's Nicola Sturgeon a close third, according to a YouGov representative sample using the ITV News daily poll app.
The App can be downloaded free for iPhones and iPad from iTunes or from Google Play for Android users.
The Ukip leader said he did not "lose my rag" when he attacked the audience during last night's televised debate for their "left-wing bias."
We watched undecided voters as they watched the debate hoping it might help them make up their minds.
Ed Miliband appeared to turn down Nicola Sturgeon's latest offer as the leaders of five "challenger" parties took part in a heated debate.