But the one thing we have all learned over the last few years is not to underestimate the SNP. One of the more amusing events of the last week or so has been various members of the Yes Alliance waking up to the fact that many of their "grass roots community organisations" were actually no more than SNP fronts. All credit to the Nats, I say. No matter what you think of them, they are not stupid. These Yes people may have been idiots but on any view they proved for a time to be useful idiots.
But that is as nothing compared to the achievement the Nats are in sight of pulling off in eight weeks. To get people to vote for them at a Westminster election without it being clear what they are voting for.
To be fair, there appear to be one thing they are not voting for. There will be no coalition between the SNP and the Tories. This is hardly surprising given the Electoral tsunami that would be likely to follow.
What the Nats would like to happen is that Labour would win a plurality but not an absolute majority in the Commons and then be kept in power by Nationalist support or abstention. In some way, they maintain, this would allow them to extract concessions although it is far from clear what the Nats would want by way of these concessions. On any view the pre oil price crash GERS figures produced this past week have, the cleverer ones know, killed Full Fiscal Autonomy stone dead. The Nats themselves clearly have doubts (to say the least) about an early re run of the referendum but in any event, even on their own narrative, that is a decision to be taken at the 2016 Holyrood election rather than the 2015 Westminster one. And beyond one or other of these objectives? No idea. I don't mean I've no idea, they've no idea.
Even the one other thing they could mention, Trident Renewal, seems much less of a red line even if it was always a pretty blurry one anyway. If a Labour Government opts for renewal who exactly were the SNP planning on rounding up to defeat that from happening? For what conceivable alternative British Government was ever going to act differently?
So what lots of Nat MPs would achieve in a positive sense is unclear. What can however be said with absolute arithmetical certainty is that the more SNP MPs there are the fewer Labour MPs there will be and the more chance therefor that the Tories will be the largest Party in the Commons.
And when you think that through, that is important.
There always has to be a Government. Even when there is a straightforward election change from one Party having a Commons majority to another, there are a few hours while the defeated Party remains "in office". When an indecisive result emerges the current administration remains in office for a longer period. If you think about it for five seconds you appreciate that's what happened in February 1974 and May 2010. Heath and Brown were still sat in Downing Street for days after they had lost their Commons majorities. They both only actually went when it was clear an alternative administration was prepared to be formed but, even had they resigned before then, it is likely they would have been asked by the Queen to continue in a caretaker capacity. For reasons of National security, never mind a myriad of other more mundane functions, executive power must be capable of being exercised by somebody.
So even if Cameron has no conceivable route to a Commons majority he won't go immediately. More to the point however is what happens if nobody else has a clear route either?
Which of the two big Parties has the more seats then becomes critically important.
If it is Labour then we can expect the formation of a minority administration. At least initially, if everybody but the Tories sits on their hands, such a Government could function as the SNP did at Holyrood from 2007-11.
But if it is the Tories?
I can't see how Labour could attempt to form a government in that circumstance. Every vote of importance would be dependent on factors we couldn't control. Obviously the SNP could be held hostage to some extent but the critical thing is that their abstention would not be enough. Since any straight Labour/Tory head to head vote would lead to defeat, one or other minority Party would always be required in our lobby and not just sitting on its hands. There is no conceivable attraction to that and, in any event, the long term electoral cost of such a guddle would be just too high. While I think Ed is right not to rule out anything if we "win", but do not have an absolute majority, it seems to me that he would lose nothing by saying that if we are not the largest Party we will not attempt to form an administration. He would only be coming to an obvious conclusion in advance.
So, what if Labour doesn't attempt to form an administration?
That's when incumbency comes back into play.
Cameron is Prime Minister and could only be removed by a vote of no confidence being passed in the Commons. Depending on the arithmetic, and the position of the remaining Lib Dems, it might well be within the capacity of Labour and the SNP to pass such a vote. In terms of the Fixed Term Parliaments Act, if no alternative administration could secure a vote of confidence within the next fourteen days then a further election would be required.
But would Labour or the SNP actually, immediately, want to trigger such another election?
This is where you need think a bit ahead.
Firstly, there is the practicality issue. In terms of the fixed term Parliaments Act the timescale for a no confidence vote and the fourteen day interregnum would require another General Election before the Summer. Would any political Party (never mind, not unimportantly, the electorate) really want that?
Secondly, Labour would at least want the opportunity for a change of leadership. If Ed hadn't won once many would argue he'd had his chance. But an immediate election re run would make that impossible.
Thirdly, on this scenario, people in Scotland would, inevitably, have woken up to the fact that the reason we didn't have a Labour Government was because Scotland hadn't voted Labour. Without any opportunity for their MPs to "show their worth" or benefit from any incumbency factor would the SNP really want to immediately (re) face the electorate in that circumstance?
So on any view the Tories emerging as the largest Party means almost certainly there would be a caretaker Tory administration at least until the Autumn.
That administration would have no "working" majority enabling it to pass anything but the most anodyne of legislation. And the no confidence route would suddenly look a lot more attractive, anyway, to a Labour Party under new management.
So actually, if you think it through, the most likely outcome of a "SNP surge" is Labour promoting a post Summer recess no confidence motion leading to another election in October. Which the SNP would need to vote for. Because if they didn't there would be no doubt who was keeping the Tories in power and Labour's 2016 prospects would suddenly look very different indeed. Sometimes you should be careful what you wish for. No matter how not stupid you are.