Addressing his party's Scottish conference in Edinburgh the Prime Minister insisted: "Let me be absolutely clear. A vote for no is not a vote for no change.
"We are committed to making devolution work better still, not because we want to give Alex Salmond a consolation prize if Scotland votes no but because it's the right thing to do.
"Giving the Scottish Parliament greater responsibility for raising more of the money it spends -- that's what Ruth believes (Scottish leader Ruth Davidson) and I believe it too.
"So here's the re-cap: Vote yes - that is total separation. Vote no, that can mean further devolution, more power to the Scottish people and their parliament but with the crucial insurance policy that comes with being part of our UK."
It was a speech more to the wider electorate outside the hall. Inside, a big majority almost certainly do not want more powers for Holyrood, and they may note he said "can" mean further devolution rather than "will".
But there is no doubt there is an unaccustomed spring in the step of those attending a Scottish Tory conference because for once this year they have the prospect of victory. With but a single Westminster seat, and with hanging on to their single European seat the best they can hope for this summer, September's referendum gives them their best hope in years for a favourable outcome.
Mr Cameron continued recent practice of playing good cop to his Chancellor's bad cop routine. This speech was much more of an exercise in love-bombing the Scots than threatening them. He called it "a big, generous, positive argument for our UK," and while his references to First World War sacrifice may not be to everyone's taste it was of a piece with his "family of nations" theme.
There was also a powerful reminder why Andy Murray is so keen to keep his views on the referendum to himself. Comments by Eve Muirhead after the Scottish curlers won an Olympic medal for Team GB saw here elevated to Tory poster girl in the Prime Minister's speech.