Dilemmas are the stuff of politics and Ed Miliband is certainly stuck on one.

While the Labour leader will rage and rail against the prospect of another five years of Tory austerity, urging Labour voters to stick to the faith - vote Labour get Labour - if the polls are to be believed, Scots do not seem to be listening.

The Ashcroft poll this week suggested how, post the referendum, the previous political reality of people voting Nationalist for Holyrood and Labour for Westminster, is beginning to evaporate.

While Labour MPs believe the polling, which consistently points to their party's meltdown on May 7, does not match the reality on the ground, their nervousness is tangible. "On the doorstep and on the street, voters," one veteran leftwinger noted, "are no longer looking us in the eye." Always a bad sign.

The dilemma Mr Miliband faces is that the result on May 7 is highly unpredictable but most experts believe it will be incredibly close.

If the Labour leader were to rule out, ahead of polling day, any post-election arrangement with the Nationalists, then he could be killing his chances of ever becoming Prime Minister and leading a government even if his party had, only just, won the most seats.

The numbers might be such that David Cameron could stay put in Downing Street, leading a minority administration helped by the likes of Ulster's Democratic Unionists and Ukip. The Tory leader's aim would be to cobble together enough support to push through a Queen's Speech and then a Budget.

The constitution means that with a deal here and a deal there, Mr Cameron could precariously continue in power. If there were a second General Election, the only party likely to have the financial wherewithal to mount an effective campaign would be the Tories.

One interesting development yesterday was First Minister Nicola Sturgeon gently removing the Nationalists' red line on Trident for doing a future deal with Labour.

While Mr Miliband might have to hold his nose, a deal with the SNP after May 7 might be the only game in town.