With the Lib Dems coming second in European elections and surging in Westminster polls, the party could hold the balance of power alongside the SNP after a snap election.
However, both Jo Swinson and Ed Davey said they would not grant the powers to hold a second independence referendum, even after a vote in the Scottish Parliament.
Mr Davey suggested the Lib Dems should aim to form the next government, not just be a part of it. “I don’t think there should be any cap on the ambitions of Liberal Democrats,” he said. “I think British politics is in the most volatile state for probably over a century.
“There is a real chance that the Conservative Party will split. There is a chance that the Labour party will split ... I don’t see why anyone seeking to be the next leader should say ‘we can’t actually run this country’.”
Mr Davey said: “Lib Dems should always be prepared to work across parties, but there are some red lines. I would not work with a Brexit Conservative party ... I cannot work with a very left-wing, Brexit-loving Jeremy Corbyn Labour Party. And I wouldn’t sacrifice the unity of my country.”
Ms Swinson said constitutional debate had “sucked the life” out of politics at Westminster and Holyrood.
“There was a white paper on independence in 2014, with 650 pages of detail, and that was rejected by the Scottish people,” she said. “When I speak to people across Scotland, there is a clear appetite for a government that makes their lives better, rather than this endless constitutional carousel that is distracting from important issues we should be getting on with.”
The two MPs will face Lib Dem members in Aberdeen today and in Edinburgh tomorrow. Mr Davey, a former energy and climate change secretary, said tackling the climate crisis was a top priority, with the aim of securing thousands of jobs for north-east Scotland in the transition away from fossil fuels.
He condemned the decision by then-Chancellor George Osborne to cancel plans for carbon capture and storage technology at Peterhead power station, claiming: “The Scottish Conservatives should hang their heads in shame.”
And with Ms Swinson, the MP for East Dunbartonshire, seen as the favourite, Mr Davey said: “The idea that anyone, from the bookies to the media, know the views of 100,000 Lib Dem members I find slightly bizarre.”