Switching arguments over who gets to govern
It is one of the more memorable moments from the 2007 Holyrood election.
After the final seats were declared, Alex Salmond, then SNP leader, addressed supporters in Edinburgh.
"I heard a rumour" he said, pausing for effect. "I think we won the election".
He claimed victory on the basis that the SNP had one more seat than Labour: 47- 46.
By the narrowest of margins, the nationalists had become the largest party in a parliament of minorities.
Mr Salmond went on to argue that in these circumstances Labour had lost its "moral authority" to govern Scotland.
Labour's coalition partners, the Liberal Democrats, took a similar view.
But in the immediate aftermath of the election, Labour's line was different.
A statement issued by the Labour group of MSPs said that "no party has the moral authority to govern without securing the support of others".
Labour's Kezia Dugdale, who is now the party's deputy leader in Scotland, was even clearer in her blog.
"If two parties form a coalition with more MSPs than the party with the single largest number of MSPs, then the views of a larger number of people will be represented in government and I think that's absolutely right," she wrote.
Fast forward from Holyrood's proportional representation election of 2007 to Westminster's first past the post contest in 2015.
The two sides seem to have swapped arguments.
SNP leader Nicola Sturgeon does not say that if the Conservatives remain the largest party they'll have the "moral authority" to govern.
Instead, she argues that if there are more anti-Tory MPs than Tory MPs the SNP would work with Labour and others to "lock David Cameron out of Downing Street".
On BBC2's Newsnight, she was asked if this would apply even if the Tories were the largest party by up to forty seats.
Ms Sturgeon replied: "If they can't command a majority, they can't be a government".
By contrast, the Scottish Labour leader, Jim Murphy, often declares that "the largest party gets to form the government".
While there is no rule making it so, that has tended to be the outcome in recent history, usually because the largest party also has an overall majority in the Commons.
You have to go back to 1923, when Ramsay MacDonald became prime minister, to find a party other than the largest party forming the UK government.
As the BBC's Douglas Fraser has noted, in the event of a "hung" parliament, the serving prime minister gets the first go at putting together a government that can win votes in parliament.
Mr Murphy seemed comfortable with this convention in 2010 when Gordon Brown sought alliances to sustain Labour in office, even though the Conservatives had won more seats.
Mr Murphy, as Scottish secretary, said his boss had the "constitutional and moral right" to try to form a government.
At that time, Alex Salmond was also expressing interest in an "alternative government scenario" excluding the Conservatives.
In the end, the Liberal Democrats were the kingmakers, choosing to negotiate a coalition agreement with the Tories.
They did so, at least in part, because the Tories were the largest party and Labour had been seen to lose the election.
The Liberal Democrat leader, Nick Clegg, has indicted that he would take a similar approach after 7 May.
He told the Financial Times, the Lib Dems would speak first to the biggest party because a "coalition of the losers" could lack "legitimacy".
"You cannot provide stability, you can't take difficult decisions, if people are constantly questioning the birthright of a government" he said.
That points to another really important factor: public opinion.
Ultimately, it is for the public to decide whether or not any particular power-sharing deal has "legitimacy" or even "moral authority".
Opinion could vary widely across the United Kingdom, depending on the combination of parties involved and the policies pursued.