Either Nick Clegg, their home-affairs spokesman, or Chris Huhne, who holds the environment brief, will make a pitch to those voters disillusioned with Labour but sceptical about whether the Tories have changed.
Nick Clegg has gone from appearing to say he knew nothing about the allegations made against Chris Rennard, the man who was the top official and key strategist of his party, to admitting he did know something whilst other party officials knew a great deal.