Up to the general election, Mr Brown and Mr Blair, personal friends as well as political soulmates since they entered Parliament in 1983, had always been teamed that way around. Mr Brown was the senior partner.
His starring performance as John Smith's deputy when the then shadow Chancellor had his first heart attack, and his effective soundbites as trade and industry spokesman, marked him in the public eye as the more heavyweight of the two, while his parliamentary colleagues voted him top of the Shadow Cabinet poll.
Only since the election campaign - during which Mr Blair became a more assertive and independent figure - and later when he more visibly carried the modernising torch and claimed law and order as a Labour issue, has the pecking order changed.
Mr Brown, tied as shadow Chancellor to a policy of deep caution so far ahead of a general election, saw his star wane. A year or two earlier - and possibly even a year or two later when economic policy was more fully developed - he would have been favourite to succeed.
His announcement not to stand won instant plaudits. Donald Dewar said it was a decision he had 'obviously agonised over', but it plainly 'enhances his position and his stature'.
His decision showed that Labour politics 'is not a just a chase for personal advancement . . . but about the cause and the building of a team that will win.'
Friends of Mr Brown insisted yesterday that soundings had shown broadly similar support for the two men among MPs, with Mr Blair marginally ahead. Trade union leaders were also dividing equally - but with much of their support interchangeable.
The pressure for Mr Brown to stand down came chiefly because of fears that a contest between the two would prove damaging, and because of opinion polls which consistently showed Mr Blair way ahead among voters - particularly among the floating vote that Labour needs to convert in the South and elsewhere.
Even a straw poll among Scottish MPs, which would have appeared Mr Brown's automatic constituency, did not show overwhelming support for the shadow Chancellor - some saying that while they felt an obligation to vote for him, they hoped he would stand aside.
Friends of Mr Brown said yesterday they feared a contest would have led their supporters to exaggerate differences between the two - possibly even creating tensions between them when their joint project is to get a modernised Labour party elected.
They also argued that the media would have damaged the party by painting the contest as one between a southern smoothie and a member of the Scottish mafia.
Union leaders praised Mr Brown for his decision. Bill Jordan, president of the Amalgamated Engineering and Electrical Union, said: 'It takes a strong, courageous and confident man to put the good of the party first.'
Nick Brown, a former member of Mr Brown's shadow Treasury team, said it was 'an extremely big decision made by a very big and generous man'.
Leading article, page 17