The Better Together campaign enjoyed what was surely its most high profile endorsement this afternoon, after Barack Obama made the case for Britain to stay together.
The US president used a joint press conference with David Cameron at the G7 to say that while it was Scotland's choice, America would prefer to see the union continue.
"There is a referendum process in place and it is up to the people of Scotland," he said.
"The United Kingdom has been an extraordinary partner to us. From the outside at least, it looks like things have worked pretty well.
"And we obviously have a deep interest in making sure that one of the closest allies we will ever have remains a strong, robust, united and effective partner.
"But ultimately these are decisions that are to be made by the folks there."
Labour's shadow foreign secretary Douglas Alexander welcomed the comment.
"I welcome President Obama's clear statement of support for UK staying together. It will resonate with many of us here in Scotland," he said.
Alex Salmond hit back: "My message to President Obama is: 'Yes, we can'."
The comment comes during a rocky few days for the Better Together campaign, after Alistair Darling was criticised for comparing Salmond to Kim Jong-il.
Salmond said Ukip's victory in securing an MEP at the European election had been assisted by the BBC's coverage, in a comment which suggested the blame lay outside of Scotland.
"It's difficult to stop a party getting foothold. We've been doing an analysis of BBC broadcasting in Scotland over this month, four-times as many broadcasts about UKIP than the SNP," he said.
"Star Trek the Original series used to have a phrase, 'beam me up Scotty', Ukip is a party that gets beamed into Scotland courtesy of the BBC."
Darling branded the comments a "North Korean response".
"He said on the BBC that people voted Ukip in Scotland because English TV was being beamed into Scotland," Darling told the New Statesman.
"This was a North Korean response. This is something that Kim Jong-il would say. And this is the same BBC for which we all pay our licence fee, and we all enjoy the national output as well as the Scottish output."
The 'Yes' camp reacted angrily to the comment, saying the Better Together campaign was lowering the tone of the debate.
"Alistair Darling demeans himself and his colleagues in the 'No' campaign with these pathetic, puerile remarks for which he should now apologise," the first minister's spokesman said.
"The debate on Scotland's future is one that deserves far, far better than boorish and abusive personal insults, as do the people of Scotland.
"Mr Darling has called for a positive debate free from abuse - he should now aim to live up to that pledge, and stop trying to divert attention from the real issues."
In a tit-for-tat exchange, the Better Together campaign pointed out the personal insults Salmond had flung at opponents.
"The nationalists have regularly dismissed people who don't agree with them as quislings, anti-Scottish and a parcel o' rogues," a spokesperson said.
"We won't take any lessons on the use of language from people who have such a proud record of slurs and personal attacks."
The exchange is particularly potent after Darling criticised the political culture of the cybernats –Scottish independence supporters online who attack anyone criticising Salmond or the 'Yes' campaign.
"When I started doing this two years ago I didn't believe you'd be in a situation in a country like ours where people would be threatened for saying the wrong thing," he said.
"Business people keep telling me that it is happening as a matter of fact. They say to me, 'We'd like to come out and support you but …'"
"It's not just the cybernats and what they do and the things they call our supporters. People in business are frightened to speak out
"I was speaking to a senior academic who told me he'd been warned by a senior Scottish nationalist that if he carried on speaking like this, it would be a pity for him. It's a real, real problem for us.
"We ought to be able to express our views without fear of the consequence," he added.
"No one wants to live in a country where this sort of thing goes on. A culture has been allowed to develop here. This is not a modern civic Scotland."
Darling said Salmond was refusing to have a debate with him over Scottish independence but that there was still time to organise one before the referendum in September.
“[Salmond] wants to turn it into a contest between Scotland and England, which is why he wants a televised debate with David Cameron," he said.
"That should not happen. I want to debate him. I’m ready to. But he’s refusing to enter into discussions with the television companies – STV, the BBC, Sky and Channel 4.
"It’s all being cut very fine. It’s not too late. I challenge him to a debate."
The UK government was criticised for creating a comedy list of things Scots could spend the extra £1,400 they would have if they stayed in the union.
The list, which contained several images of lego men taking part in activities was dismissed as patronising and juvenile.
However, the concerns of many unionists that the 'Yes' campaign were about to pull ahead in the polls appear to have come to nothing.
An Ipsos Mori poll for STV showed 52% planning to vote 'no', 34% 'yes' and 13% undecided.