Speaking at the Lib Dem conference in Bournemouth, Mr Clegg, who stepped down as leader in May, suggested the party would fill a hole in the centre ground of British politics.
He said: "In that huge chasm between a self-serving Tory government and a far-left Labour opposition lies our great opportunity.
"There is a place in British politics for an open-minded, outward-looking, optimistic party.
"Because - as dawn follows the darkest hour - there is now space in British politics for a great fightback by the most resilient political party of our times, the Liberal Democrats."
Back in May, the Lib Dems lost 48 MPs including a number of government ministers. In the following weeks Christian MP Tim Farron was elected leader.
Speaking about the party's future, Elizabeth Jewkes, acting chair of the Liberal Democrat Christian Forum told Premier it's not all doom and gloom.
She said: "We were completely devastated on May 8 but personally I was really cheered when I got an email that said 'We had a terrible night - but 690 people joined the party overnight'.
"These emails didn't stop coming and the members didn't stop coming and our membership has grown by around a third."
The conference comes to a close with the Leader's Speech on Wednesday afternoon.
Listen to Elizabeth Jewkes speaking to Premier's Political Editor Martyn Eden: