The Liberal Democrats are stronger and more relevant than ever following the British electorate voting to leave the European Union, leader Tim Farron is expected to announce at the start of the party's conference.
He will claim his party, which has vowed to do all it can to keep the UK in the EU, is the only one lobbying for an "open, tolerated, united" country.
Farron is also expected to use Labour's recent divisions as ammo for his argument that his party gives liberals a "home".
Despite having only eight MPs, the party has seen a surge in membership numbers.
Supporters will flock to a four-day event that kicks off today (17 September) in Brighton, with the party having attracted 10,000 new members since the EU referendum. In contrast, Labour received 128,000 more members in the two weeks following the EU referendum.
In an address to the rally, Farron will outline plans to park "Lib Dem tanks on the Conservative lawn".
He is also expected to highlight the Conservative party's disorganisation in dealing with the aftermath of the Brexit vote.
Capitalising on the ongoing divisions within the Labour party, he will make a move to position the Lib Dems in the minds of voters looking for a viable opposition to Prime Minister Theresa May and her party.
He is also expected to criticise newly elected Ukip leader Diane James who he will claim leads a party whose policies are "based on a vision for Britain that is closed, hateful and divided".
He will say: "This party stands stronger, large, determined, relevant, in the right place in the right space at the right time.
"Just when Britain needed a movement that will challenge this Tory Brexit government, just when liberals in other parties are desperate for a home where they can make a difference, the Liberal Democrats are back and we matter more than ever."
Farron will give his traditional end-of-conference leader's address on Tuesday.
On Saturday's agenda, debates will be held on homelessness, corruption and corporate crime, along with consultative sessions on nuclear weapons and sex work.