Thirty years ago, a talented young Labour backbencher by the name of Neil Kinnock was offered a job as a junior education minister in Jim Callaghan's government. He turned it down, and some thought he would see out his career as a member of the left-wing awkward squad alongside the likes of Denis Skinner and Willie Hamilton. Instead, six years later he was leader of the Labour Party.
Last week, the talented backbencher Jon Cruddas, who came a creditable third in Labour's deputy leadership election, rejected the offer of a government job from Gordon Brown. Explanations vary, but the consensus among Labour-watchers seems to be that Gordon offended his amour propre by not offering him a more senior role.
I supported Cruddas for the deputy leadership, and was glad to have done so. In my opinion he lost the election but won the campaign - much as Kinnock was said to have done in the general election of 1987.
That said, I think he has made a serious mistake by refusing Gordon's offer to join the government, one which, unlike Kinnock, he will come to regret.
I have no doubt that what scuppered Cruddas was Gordon Brown's decision to award the job of party chair, as opposed to Deputy Prime Minister, to the victorious candidate, Harriet Harman. Cruddas was patently running for the job of party chair throughout the election and, had Harman been given the DPM role, the job could still have been his.
Alternatively, he could - and should in my view - have been made Housing Minister having done so much to put the issue of affordable social housing on the agenda during the course of the campaign. But the inexplicable non-promotion of Yvette Cooper meant there was no vacancy in that role.
In the light of these unpalatable truths, Cruddas really should have swallowed hard and accepted whatever he was offered - apparently a Labour vice-chairmanship reporting to Harman coupled with a regional ministerial brief.
But he walked away from the opportunity to serve a Prime Minister who is currently carrying all before him, and having turned down Gordon once, I personally think it is unlikely he will be asked again.
So what now for Cruddas? Well, the Kinnock parallel is again instructive. Had Labour won the 1979 general election, it is inconceivable that the Welshman would have become party leader in 1983. Denis Healey would have inherited, and eventually the leadership would have passed to a right-winger like Roy Hattersley or John Smith.
In other words, it was Labour's defeat that allowed Kinnock to come to prominence in the early 1980s, as a fresh face untainted by association with what, at that time, was a much-reviled administration.
In the same way, if Jon Cruddas is to remain a major figure in the Labour movement, and if his critique of New Labour is to retain any potency, it will almost certainly require Gordon Brown to fail in his mission to renew Labour in office and secure that unprecedented fourth term.
Is Cruddas really playing for such high stakes? Or has he simply allowed his pride to get the better of him?