The Vince Cable story
Sir Vince Cable could stand down as Lib Dem leader as soon as next yearand wants the contest to replace him to be opened up to non-party members.
In a speech later, he will set out plans to transform the party into a "movement for moderates".
Party sources say he wants to see this delivered while he is still leader and wants to stay in his job for crucial Brexit developments.
He also wants to continue campaigning for a second EU referendum.
"He has a set of objectives rather than a timeline," a senior Lib Dem source said.
The Lib Dems have 12 MPsdown from the 57 they had in 2010.
The party has struggled electorally since 2010, when it formed a coalition government with the Conservatives and remains in single figures in the opinion polls.
Sir Vince has predicted a realignment of British politics, as Labour and the Conservatives split over Brexit and it is thought he wants to ensure the Lib Dems, who are campaigning for a second EU referendum, are well placed to work with any new "centre ground" groups.
In his speech, he will urge the party to back plans for a "supporters' scheme" aimed at giving 200,000 online supporters more of a say in the party's direction.
But any changes would have to be approved by party members and will be discussed at their conference in Brighton later this month.
Sir Vince took over as leader in July 2017 without a contest following the resignation of Tim Farron.
As stated by pre-released extracts from his speech, the former business secretary will urge the Lib Dems to introduce a supporters' schemeto mobilise more "moderate, liberal-minded voters" in campaigns such as opposing Brexit.
The party had 99,200 members as of August 2018. Sir Vince will say: "We should widen membership with a new class of 'supporters' who pay nothing to sign up to the party's values.
"They should enjoy a range of entitlements, including the right to vote for the leadership and to shape the party's campaigning online."
The party should be in "constant conversation" with "the vast swathe of voters in the centre ground whom we are yet to persuade", he will say.
"Groups like More United, 38 Degrees, Avaaz and Change.org have shown us how these regular conversations can happen, how we can engage hundreds of thousands of people online.
"I want our party to do that and to offer our movement a political arm within Parliament. So it is not just a protest group banging at the door, but a movement with a voice on the insideour parliamentary party."
The Labour Party changed its membership rules under Ed Miliband from an electoral college system in which union members, MPs and party members had one-third of the vote each to a "one member one vote" system, which allowed "registered supporters" to take part for a £3 fee.
Labour's membership swelled in 2015 and it is thought to have had about 540,000 members as of April 2018, up from around 190,000 in 2014.
But there were claims that the new rules were fuelling "entryism"allowing other groups to infiltrate the party in an effort to promote their own agenda.
Sir Vince will say: "The Liberal Democrats are not a socialist party concerned with extreme-left entryism or a right-wing party trying to keep out extreme right-wingers. We are a centre ground, pro-European, liberal and social democratic party, welcoming like-minded supporters.
"This will be a movement for moderates."
It is thought that Sir Vince plans to rewrite the rules so that supporters need to be enrolled for 12 months before voting, to prevent infiltration by rival parties.
He is hoping to emulate the success of Justin Trudeau's Liberal Party in Canada, which leaped from third place to victory in 2015.