From my school science lessons, I recall that the thing about pendulums was that they swing back and forward with equal velocity.

So, with the polls suggesting that the electoral pendulum has swung pretty strongly in the direction of the SNP, it is maybe timely to consider the ramifications of this movement.

The first caveat, of course, comes from history: polls can be wrong - or even unhelpful. The poll which showed a "Yes" majority before the September Referendum is sometimes credited with stiffening the "No" vote. Before the 2011 Scottish parliamentary elections, the suggestion was that the SNP would be significantly defeated - but the actual result was a clear majority.

However, it seems likely that the SNP are going to do well in the General Election - though just how well is still a matter of conjecture.

For the first time in its history, the party could find itself with an element of power within the UK Parliament, as well as being the devolved government of Scotland - a situation which can be expected to continue past the 2016 Scottish elections.

With such power comes responsibility and accountability. When you move, from being the underdog and outsider, to a position with, at least, partial input into major decision making, there is a change in the way in which you are regarded by the voters and the public in general.

Nearly two terms into governmental office in Scotland, the SNP appear to have pleased most of the people most of the time, and substantiated their claim to "stand up for Scotland", at least in the eyes of the majority of voters.

However, as the Redmondite Irish Parliamentary Party discovered, and as JFK memorably put it, "Those who foolishly sought power by riding on the back of the tiger ended up inside." In the last Parliament, the Liberal Democrats made an art form of demonstrating this reality, and that is one reason why the suggestion of a post election 'coalition' with Labour would never be entertained by the SNP.

For all that, a vote by vote, "confidence and supply", agreement still holds its dangers, and the SNP can be sure that any such arrangement would be manipulated by the establishment parties to ensure maximum potential embarrassment and difficulty for the "interlopers".

In addition, another term in Scottish Government, allied to a tranche of MPs, would move the party closer to the position of hegemony in Scotland which formerly "belonged" to the Labour party. That position and its ensuing sense of entitlement, has clearly contributed, along with other circumstances, to that party's decline in electoral fortunes: the "party of the underdog" is now viewed by many as a self serving part of the establishment.

It has taken the SNP a long time to move from outsiders to agenda setting, and the signs, so far, are that they have learned their lessons well. Hard work on the streets and connecting with the electorate has been a vote winner, and, combined with a broadly socially democratic approach, has chimed with people's demands.

The Referendum campaign allowed the SNP and others to convince voters in Scotland that they can have impact on the political scene, and suggested that the power base in London knew little and cared less about the concerns of folk north of the border.

Over the coming years, the SNP will be judged on their stewardship of the trust they have gained from the Scottish voter, and their ability to promote and enact the changes the electorate wish to see.

The signs are that Nicola Sturgeon and her colleagues are well aware of this, and they may just have the commitment and ability to succeed in their mission to minimise the swing of that pendulum.