Scottish Tory leader Ruth Davidson has "absolutely" ruled out supporting an SNP government in Edinburgh if the nationalists fail to win a majority in next year's Holyrood election.
Westminster parties have rounded on the SNP insisting the party will cost the rest of the UK dearly and push for another independence referendum.
From my school science lessons, I recall that the thing about pendulums was that they swing back and forward with equal velocity.
That old air of haplessness still hangs around Sir John Major.
Few could have predicted the series of events that led the SNP to make such a mark on the UK General Election, and for it to use its position to court Labour rather than pursue constitutional change.