The Liberal Democrat leader is under intense pressure to deliver a strong speech to bolster his authority and reassure MPs that he remains keen to lead the party forward.
One senior MP said: "This is a very important speech for Charles. He has got to pull out all the stops."
In his annual address to the party conference, Mr Kennedy will speak frankly about his motivation and his vision for the party. He will focus on the definition of Britishness, making the case for multiculturalism. One source close to Mr Kennedy said: "It's a departure from the usual type of speech he makes. This is going to be about what he is about. It's very personal."
Mr Kennedy's leadership style came under fresh attack yesterday after he was accused of failing to support his own frontbench team who have suffered a series of defeats this week at the hands of grassroots activists.
He was blamed for not speaking during two high-profile debates about Europe and a proposal to part-privatise the post office and for "letting Vince Cable and Norman Lamb hang in the wind".
There is little prospect of activists forcing Mr Kennedy to resign because of his personal popularity. But there was renewed talk yesterday in Blackpool of what would happen if Mr Kennedy resigned before the next election.
In a BBC interview, Simon Hughes, president of the Liberal Democrats, revealed he had had two meetings with Charles Kennedy since the general election in which he reassured him "he would never stand against him". But he expressed his desire to run for leader if Charles Kennedy were to stand down.
Mr Hughes told Radio 5 Live: "I have said to Charles, to him personally, he knows this, that I would never stand against him. I have given him a personal assurance that I would never stand against him.
"If he was to stand down of his own accord that's a different question."
Mr Hughes added: "I hope he was relieved and grateful and reassured."
Mr Kennedy's spokesman said there was no reason to be "reassured" by Mr Hughes and brushed aside criticism of the party leader.
Mark Oaten, the party's home affairs spokesman, also launched a impassioned defence of Mr Kennedy and said he was irritated by continuing criticism of him. He said Charles Kennedy had his "full confidence" and was "a superb leader".
But he added that if Mr Kennedy "decides at some point to step down" he would "think about" running as leader.
Today Mr Kennedy will adopt a more aggressive tone, launching an attack on Tony Blair over Iraq. He will say Mr Blair's "pride" and "blind support for George Bush is continuing to cost lives". He will accuse Mr Blair of "denial" and failing to find "a solution".
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