[joeysteele]

He doesn't need to do any deal at all, really the SNP have said clearly loads of times, they will not allow a Conservative govt; to be in power if they have the numbers to prevent that.
Alex Salmond and Nicola Sturgeon know,if they did anything that brought that about,then they too would pay a heavy price for that with Scots voters afterwards.

If after May 8th,it is clear the Conservatives have not got the support from other parties in parliament to get a Queen's speech passed, then it will be up to Ed Miliband to put forward a Queen's speech.
Which he can easily do as a then minority Labour govt:

The SNP then have to decide with no talking to Labour at all,whether they will support that Queen's speech or vote aginst,which would then open the door to David Cameron trying to get one passed,which the SNP could never ever support,
That would then open the door to a new general election.

The SNP have the Holyrood elections next year,no way would they want another general election, finances will be stretched to the limit.

Ed Miliband, then only needs to call the bluff of the SNP as to the Queen's speech vote,without any deals whatsoever and last night he indicated clearly,he would rather not take office than do a formal deal with the SNP.
So a likely new general election would be the outcome if the SNP have the numbers to prevent both parties governing.
He rarely ever changes his mind on things once he rules them out.
He has now ruled out coalition and confidence and supply too.

Would the SNP really not support a Labour Queen's speech over a Conservative one,I think not and once they have supported it then they couldn't really in the future vote against the major contents of it.

I see nothing wrong with Labour doing a deal with the SNP, if the Scottish part of the UK elects large umbers of them to Westminster.
I would welcome a deal, however he has stated, it would be a minority Labour govt; he would lead.

It is then for the other parties to decide, do they allow him to govern or bring him down and allow the Conservatives into power,or force another geeral election.

For the SNP, that really could be political suicide if they brought that about.
It is in fact in the scenario above, Ed Miliband who has the upper hand as to the SNP no matter what occurs in Scotland on My 7th..