The Liberal Democrat conference will begin today with leader Tim Farron eager to woo Labour voters and MPs concerned about the direction the party has taken under Jeremy Corbyn.
Mr Farron hopes that Labour's shift to the left under Mr Corbyn will open up space to allow the Lib Dems to offer a "credible" alternative to Tory rule.
The Lib Dem leader has claimed "distressed" Labour figures have already contacted him since Mr Corbyn's election and will assert that his party can offer a home to disaffected liberals in other parties.
The party will gather in Bournemouth on Saturday to discuss how to move forward following the electoral mauling which saw it lose all but eight of its 56 MPs in May, triggering Nick Clegg's resignation.
In his first conference appearance as leader, Mr Farron will attempt to rally the party's activists, insisting that the surge in membership since the election is the sign of a fightback.
At the conference's opening rally, he will say: "Britain is teeming with liberals, some of them are not yet in the Liberal Democrats. Some of them are in other parties. But we are their home."
The party's membership has grown by 20,000 to 61,000 since the election, with a record 2,500 members expected at the conference.
Highlighting the new members, Mr Farron will say: "By their simple act of joining us they proclaim that fear and division will not win, that liberalism can and must win."
The Lib Dems believe that Mr Corbyn's victory and the Tory policy agenda since the end of the coalition means there is a space in the centre ground they can fill.
In a sign that he does not believe Labour can win the next election under Mr Corbyn, Mr Farron will say: "We once again see the prospect of a decade or more of Tory rule, and it fills us with dread.
"So we have no right to sit in a comfort zone, every family whose home is at risk because the Tories undermine the recovery that we built; every desperate refugee turned back at the port; every business facing ruin if we leave the EU, every one of them is depending on us.
"We are liberals, we correctly talk a lot about rights, but we have a duty. Our duty is to claim the mantle of the credible progressive alternative to the Tories."
The Lib Dem leader, who will face a test of his authority at the conference by opposing a motion calling for the UK to give up its nuclear deterrent, risks another row with the grassroots over aviation policy after indicating he could back expansion of airports around London.
Party activists had previously ruled out airport expansion in south-east England.
But while Mr Farron maintained his opposition to an extra runway at Heathrow he said he was "open-minded" about other options for increasing capacity around the capital.