Peter Mandelson's decision to run has surprised colleagues

Key Party Test for Mandelson

Most interest will inevitably fall this year on the high-risk bid by the Minister without Portfolio, Peter Mandelson, to win a place. His move is being interpreted as an attempt to legitimise his power as chief strategist and Government troubleshooter.

Success by Mr Mandelson, a close confidant of Mr Blair, would make it harder for critics to claim that he is in his position of authority purely because of patronage. It has been reported that his high-profile campaign has been boosted by the background support of the Deputy Prime Minister, John Prescott, with whom he has clashed privately in the past.

Now the party has won power, the Chancellor Gordon Brown has given up his NEC post, one of seven in the constituency section. And the Home Secretary, Jack Straw, who narrowly missed winning a place last year, is also not standing this time round.

Ken Livingstone is looking to go one better this year

This leaves left-winger Ken Livingstone, who came close behind Mr Straw in last year's poll, as Mr Mandelson's main rival to take over the vacancy. Attention is also bound to focus on whether the popularity of the Foreign Secretary, Robin Cook, who has topped the constituency section for two years running, has been dented by his recent decision to leave his wife of 28 years.

Ballot papers for the NEC elections, in which all 400,000 party members have a vote, will go out on Wednesday. Usually about a third of ballot papers are returned.

It will be the last NEC election under the current rules. By next year the party's "Labour Into Power" reforms will be in place. This will mean separate sections for MPs, Cabinet ministers and constituency parties, and the scrapping of the women's section.