Shadow Education Secretary Tristram Hunt is likely to throw his hat into the ring for the Labour leadership on Wednesday 20 May in a speech in which he will attack Ed Miliband's "timid" rejection of radical ideas.
While defeated former leader Miliband pursued a 35% strategy - focusing on core Labour voters and disaffected Lib Dems and hoping UKIP would sink the Tories - TV historian Hunt will say Labour needed a "100% strategy" that was "broad-based" and "forward-looking".
Four candidates have so far put their names forward to succeed Miliband, and each needs the support of 35 Labour MPs in order to take part in the contest, which will be decided before the party conference in September.
Andy Burnham, Yvette Cooper, Liz Kendall and Mary Creagh have all declared their intention to stand. Chuka Umunna, the favourite, announced his intention to stand only to withdraw it within three days, citing concerns about media scrutiny of his family.
In a speech in London, Hunt is expected to say that the party was too timid and tied itself up in a "strategic strait jacket". It also lacked the "political courage" to make the case for its ideas to reduce inequality and promote economic regeneration.
"Not since 1983 have we been so out of step with the prevailing mood of the nation," he will tell an event at the cross party policy think tank Demos.
"But worse still, for perhaps the first time, we now face an electoral battle across three distinct fronts: the rise of nationalism in Scotland, a lack of trust in our traditional English heartlands and loss of confidence in Middle England."
He is expected to suggest freezing or reducing child benefit for school-age children to pay for a "universal right to free childcare" for all parents of two-year-olds and giving benefit claimants with a "strong record" of employment higher levels of out-of-work payments.