Party leader Nick Clegg will seek to rally his rank-and-file by claiming that now is the time for the Lib Dems to supplant Labour as the main "progressive" party of British politics.
His allies insist that the party, going into its last annual conference before the next election, is optimistic about taking on both Labour in the north and the Tories in the south.
Yet the Lib Dems' average poll ratings remain stubbornly lower than 20% - down on their 22% showing in 2005 and trailing Labour by about 10 points in the most recent surveys.
Joined by Charles Kennedy, who led the Lib Dems into the 2005 election and who remains popular with the grassroots, Mr Clegg will want to buoy his troops at a first-night conference rally this evening.
He has set out, on the eve of what could be a defining conference of his leadership, his ambition for the Lib Dems to become the main alternative to the Tories.
Describing Labour as a "spent force", Mr Clegg wrote in a pamphlet this week: "The choice for progressive voters at the next general election is now between the Liberal Democrats and a Conservative Party that parrots the language of change to maintain the status quo.
"Liberalism is the ideology most suited to this age and the Liberal Democrats are the party now offering the rallying point for progressive politics in Britain."
But such positioning, while clearly intended to steal votes from a weakened Labour Party and distinguish Mr Clegg from the Conservatives, could also serve to alienate Lib Dem voters on the right of the spectrum.
The Tories, already buoyant in the polls and more of a threat to Lib Dem votes than for many years, sought to increase that threat yesterday with a naked appeal for defectors from the third party.
Leading Conservatives have been insisting they, too, have "progressive" credentials and Tory chairman Eric Pickles claimed there had been a "steady stream" of Lib Dems joining his party.
He unveiled the latest as James Keeley, a former Lib Dem parliamentary candidate.
"From the Factory Acts to 42 days' detention, the Conservative Party will always be the home of progressive liberal democracy in British politics," Mr Pickles said.
As well as the risk of attrition to the Tories, the Lib Dems will be mindful that traditional Labour voters will be wary of proposed Lib Dem cuts in public spending - an issue that promises to take centre stage at the next election.
While Prime Minister Gordon Brown has acknowledged the need only for cuts away from the public services frontline, Lib Dem economics spokesman Vince Cable has spelt out more brutal plans.
He called this week for a much tighter fiscal squeeze than Labour has pencilled in and, crucially, that all areas of spending need tackling to bring down the UK's debts.
A list of specific proposals included freezing overall public sector pay and bringing pensions more into line with those available to private employees.
"This process will be painful and difficult," Dr Cable wrote. "It will involve real cuts in many areas and will mean that the big budgets - health, welfare, defence and education - must be tackled."
Labour supporters might be alarmed by such language, but Dr Cable and other similar Lib Dems are hedging that honesty with the voters will play best for them.
In a dig at the Labour and Tory parties who have been careful not to detail much of their spending plans, Dr Cable said: "Politicians must not shy away from explaining in detail how they will tackle the problem of deficits and debt."
One of the perennial questions facing Lib Dem leaders is perhaps now more pertinent than it has been for many years - who, if anyone, will they team up with in the event of a hung Parliament?
Mr Clegg will doubtless do his best to bat away any such questions this week, insisting the Lib Dems are fighting for themselves alone in the forthcoming election but refusing to rule out any particular scenario.
But his Demos-published pamphlet this week left little doubt that he sees the party as more ideologically opposed to the Tories than Labour.
And the more strident and personal his attacks on the Tories become - he will today describe David Cameron as a "con man" - the more difficult it will be for him to enter a coalition government with the Conservative leader.
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