By Laurence Durnan, from Political Scrapbook

As Labour’s leadership marathon reaches its final furlong (and hacks exhaust supplies of sporting metaphors) tonight’s special Question Time debate may be the last opportunity to impress dwindling numbers of undecided voters. But while candidates’ spiel may feel shopworn, changing fortunes, campaign themes and public perception since May should not be overlooked.

"When votes hit the doormats on 2 September he’ll be the finished package," one of Ed Miliband’s team told me, describing their "X-factor strategy" for the candidate many thought would add fraternal interest to a contest which was a foregone conclusion. While Ed has certainly gained ground on his brother he might not, in relative terms, be the biggest net benefactor. At the beginning of the year, the suggestion of Diane Abbott as a serious contender for a place on Labour's frontbench would have left much of the PLP barely able to contain their mirth. But even her critics would acknowledge that Abbott's stock has risen, leaving her (should she choose to run) within touching distance of success in the shadow cabinet elections.

Similarly, Ed Balls' humanising efforts to jettison his TeeBee-GeeBee baggage have been largely successful. His incisive attacks on Michael Gove have won him many fans and while this may not translate into votes (the latest polling suggests he may come fourth), the exercise in political rehabilitation has been worthwhile, confirming him as a force that the right ignore at their peril.

With his unforced easy manner impressing former Labour voters, Andy Burnham’s victory in Newsnight's focus group came too late to shift attention from the fact of his northern-ness as much of the electoral college had already voted. But Burnham’s "I’m not from London" campaign cul-de-sac was of his own design and it is here we see campaign revisionism underway in earnest.

"Actually my pitch hasn't been that I'm from the north ... People just choose to hook me in that bracket because of my accent," he told Progress this week. Oh, really Andy? Launching his candidacy on the Andrew Marr Show in May, the first words out of Burnham’s mouth were: "My background is different. As people can probably hear I come from a different part of the country!"

Having exchanged his wonk geekiness for statesman gravitas some time ago, David Miliband was, presentationally, by far the most polished contender. Though less charitable comrades might suggest his leadership campaign predates the general election, the consistency of his message throughout owes more to the discipline of his team in sticking to their key themes.

As to whether we will hear anything new this evening, this observation from the older Miliband is instructive: "We’ve listened to each other’s speeches so much I could give one of the other ones."

This blogger hopes they can surprise us.