Speaking before Scottish LibDems arrive in Aberdeen today for their spring conference, Willie Rennie said the theme of the gathering would be that they are promoting Scotland in the UK and also the UK in Europe.
Mr Rennie believes delivering these clear messages will help the party overcome its low standing in the polls - an ICM poll this week had the Lib Dems as low as 5%.
He said: "Through good and bad these relationships are never perfect but we recognise that working in partnership in a choppy world is a better thing to do, looking after your neighbour as much as looking after yourself is an important Liberal value."
Acknowledging the Scottish LibDems may be paying a heavy price for being in coalition with the Conservatives he said: "There's a chunk of people who voted for us in 2010 who are sitting and waiting to make an assessment about where they go next. These people are not showing up in the polls in support of us, but they aren't lost to us.
"When the next decision point comes in the run-up to the next General Election these people will have to make a choice. Do they want a party that represents them locally very well as MPs, but also holds the Government to the centre ground of our politics?
"I think the combination of the powerful local advocate and that unique national message will convince those undecided people that it's time to return to us, but their faith in us has been shaken and we have to prove to them that we are worthy of their support."
He believes that will help them retain their single European seat in June, citing their pro-EU credentials and the rural popularity of MEP George Lyon, and their 11 Westminster constituencies the following year.
He points to the achievements of the Westminster coalition on tax cuts, pensions, jobs and economic recovery, plus Holyrood achievements on childcare, polic-ing and the scrapping of corrobor-ation, classic civil liberties issues.
But the current polling points to the toxic effect of being in bed with the Tories. In a reply which will doubtless be echoed again over the weekend, starting with Nick Clegg this afternoon, he said: "There's no doubt it has damaged us but you don't go into politics just to blow with the wind.
"If we didn't make the right decision back in 2010 to go in with the Tories, to provide stable government to get the economy back on track, I don't know where we would be now.
"We could have played politics in 2010 and just looked after ourselves and we might have been made to look more popular, but I know it would have been the wrong thing to do. To get into politics you need to try to make a difference."
Mr Rennie expressed only mild disappointment with Labour's plans for more devolved powers, saying they had come a long way in the last couple of years. Of the prospect that the three pro-Union parties will reach common ground in time for September, he said: "It would be helpful but not vital."
Two former senior party figures, former chief executive Andy Myles, and former treasurer Denis Robertson Sullivan have endorsed the Yes campaign.
Mr Sullivan said: "Indepen-dence is the key to responsible co-operation both within these isles and Europe.
"The European Union and its growth means we have an overarching umbrella which embraces nearly all European countries and means all of us can be independent yet work and share together."
SNP MSP Chic Brodie, a former Liberal Democrat, urged others in the party to follow the lead of Mr Myles and Mr Sullivan.