Lib Dem leadership hopeful Sir Menzies Campbell claims he has the backing of more than half the party's 63 MPs, as the campaign enters its last full week.
Sir Menzies is calling for constitutional reform
He received the support of John Hemming (Birmingham Yardley), bringing his backers to 32, a spokesman said.
Sir Menzies has argued for constitutional change, with elected peers and more powerful local councils.
Simon Hughes and Chris Huhne have called for more focus on green issues, ahead of hustings in Manchester.
'Give power away'
The 73,000 Lib Dem members have until 1 March to vote for a replacement for Charles Kennedy, with the result due the next day.
Ahead of the Manchester hustings, Sir Menzies, the party's acting leader and foreign affairs spokesman, said: "I want to win power, so that we can give power away. I want us to be the champions, again, of people power.
"I want to see citizens able to initiate inquiries, ask questions direct of decision-takers and have petitions debated... in short, people power to replace unelected quango power so that government is servant and not master."
He is calling for proportional representation in all elections, an elected House of Lords and control of the running of schools, hospitals and transport to be handed to local government.
Sir Menzies is also demanding a civil service with its "independence guaranteed" and a more "robust" Freedom of Information Act.
Mr Hughes, the party president, is calling for a "freer, fairer and greener Britain".
At the hustings, he will pledge to repeal ID cards legislation and tackle social injustice and inequality "at home and abroad".
Mr Hughes said: "Although the race is close, the evidence is that I have a slight lead with the other two battling it out for second place."
Meanwhile, Treasury spokesman Mr Huhne said he would increase taxes on emissions.
The UK could be a "big loser" if climate change trends continued, he added.
The bookmaker Coral has Mr Huhne as the favourite to win, on 4-6, followed by Sir Menzies at 5-4 and Mr Hughes at 9-1.