SirChenjin .... who do both the Labour and SNP Party's hate more (the Conservatives), and I suspect that Miliband's won't do A deal with the SNP, is Oxbridge Student Union Debating Society tricksy - as to get anything through a 650 MP Westminster, a Labour Party (with similar 275 ish seats expected as the Conservatives) NEEDS a 57 ish Westminster seat SNP, to get ANY legislation through.
BOTH Labour and the SNP offer voters independently; LESS budget deficit reduction, MORE debt driven pending and MORE taxes - so who needs to publicly 'agree' on that direction of travel and individual piece of legislation?
Mr Miliband and Mr Salmond (Ms Sturgeon's Westminster deputy) don't even have to wink at each other, as they vote en block.
Mr Miliband can say "I won't become PM if it means an agreement", but knows that when Labour opposes all Conservative legislation as they have done so for the past 5-years AND Ms Sturgeon (and Plaid Cmyru) has guaranteed that they will NOT vote with a minority Conservative government - Cameron can not be PM either.
So just wait until there is parliamentary paralysis from May 8th, and a Mr Miliband KNOWING he has the SNP block vote in his pocket, stands up and says 'I know what I said citizens, but I have to go back on what I said, for the good of the Uk'.
(pass the sick bag, somebody)