Tim Farron has confirmed he will run to be the new Liberal Democrat leader.
Mr Farron joins former health minister Norman Lamb as the contenders to replace Nick Clegg following the party's disastrous general election results.
The "debacle" of the Liberal Democrats' U-turn on university tuition fees "massively undermined" voters' trust in the party, one of its leadership candidates has said.
Norman Lamb said the Liberal Democrats had learned an "extremely painful lesson" from raising tuition fees to £9,000 while in coalition government with the Conservatives, despite ex-leader Nick Clegg's pledge to vote against any increase.
"Trust for me is critically important and that debacle massively undermined people's trust in the party," he told BBC Radio 4.
"I believe very strongly that we have now learned a massive lesson, an extremely painful one. But I don't think we will ever make that mistake again."
Lamb - who confirmed to ITV Anglia yesterday that he wanted to replace Nick Clegg - voted in favour of tuition fee increases in 2010, while his potential rival for the leadership, Tim Farron, rebelled and voted against the policy.
The rapper told his 859,000 followers on Twitter that he was a fan of the North Norfolk MP.
Nick Clegg has resigned as leadrer of the Liberal Democrats after the party suffered their worst General Election collapse in years.