After his four months as Finance Minister of Europe's biggest economy, his legacy is that of rising unemployment and falling output.
Other Socialists might stop for a moment to ponder why such things were happening, but not "Oskar". He will go on, for the rest of his life, blaming the gnomes of Frankfurt, international currency speculators, and "unfair" - meaning "too low" - taxes in other European Union countries.
We know, because Mr Lafontaine has been here before. In 1990 he was the champion of the Social Democrats against a poorly regarded Helmut Kohl. He lost, but it took some doing, forfeiting as he did the biggest lead a party had ever enjoyed in German electoral history.
But Mr Lafontaine was right, as he is happy to tell anyone who will care to listen. He had criticised Mr Kohl's formula for bringing the freshly free East into the Federal Republic. The costs, he pointed out, would be enormous. "Nonsense" retorted Mr Kohl as he proceeded to promise "blooming landscapes" in the East within a few short years.
Mr Lafontaine was right, but no one in those heady days wanted to listen to a chubby Cassandra. He lost because he was seen to be carping about the German nation's most glorious moment since the end of the Second World War. He was the man, it appeared, who was opposing re-unification.
That year had been a terrible one for Mr Lafontaine. While campaigning for those elections, he had been stabbed in the neck by a deranged woman. The ambulances took a long time coming, as the chancellor-candidate lay in a pool of his own blood. He very nearly died.
Still, the plucky little man from Saarbrucken - lampooned for his looks and haughty demeanour as "Bonaparte of the Saar" - soldiered on, digging his political grave deeper every step of the way.
When the dust eventually settled on those elections, Mr Lafontaine retreated to his home region, seeking solace from his role as the Prime Minister of Germany's least significant Land. He fell into a depression - for a long time sipping more of his beloved Burgundy than he perhaps should have - and faded from the national picture. But then, slowly, he clawed his way back.
On the leftist firebrand circuit, there is no one quite like him. Even in those dark days, Mr Lafontaine could wrap a crowd around his fingers in an instant. But surely, the people said, he would not come back to national politics.
He did, pouring into a vacuum at the top of the party in 1995. In the interim, other Social Democrats had had a go against Mr Kohl and been burnt. Mr Lafontaine felt ready for the second round.
It did not happen, because of a certain Gerhard Schroder, who many in the party felt did not have much to offer, except the prospect of victory.
And so the comrades weighed up the pros and cons: Mr Lafontaine would be good for socialism, they thought, but only if he were elected. By this time last year, it was clear that Oskar's sex appeal was limited to a narrow section of hardcore SPD supporters.
Their votes alone could not dislodge Mr Kohl.
It must have been bitterly disappointing for Mr Lafontaine to hear this kind of advice from his closest friends. Confronted with Mr Schroder's electoral pull, he stepped out of the ring.
The rest might have been history, except that Mr Lafontaine refused to draw the correct conclusions.
He treated the party's electoral triumph as a personal victory. Now was his chance to implement the kind of socialist vision he had been dreaming up over the past decade, aided by his wife Christa Muller, an arch-Keynesian economist.
Thus did Germany end up with a nightmare ticket of a centrist Chancellor lacking any substance, and his leftist deputy having too much of the wrong kind.
He did, however, render one useful service. As chairman of the party, he kept leftist critics at bay. With him gone, there is no one to deflect the wrath of the party, forever suspicious of Mr Schroder's "New Centre". And Mr Schroder has nowhere to hide.
The Chancellor looked stunned last night as he presided over the shortest press conference of his life. Today the party leadership is to choose Mr Lafontaine's successors, for it is unlikely that any one person can fill those two vacancies - at the head of the party and the finance ministry.
Mr Schroder will now try to grab the chairmanship of the party. But whether he succeeds or not, it will be a lot harder from now on to keep the rank and file in line.Reuse content