Six months ago, the Social Democrats (SPD) had an apparently unassailable lead over Mr Kohl's Christian Democrats (CDU). Now, seven weeks away from elections, the situation is reversed. Polls show the CDU 5 percentage points ahead of the SPD. In an interview with the the Independent, Mr Scharping, 46, acknowledged the party's mistakes. 'That's absolutely certain. Between March and the summer, we didn't make things clear enough.'
Mr Scharping, who became party leader last year, instilled order in the party's ranks, and was seen as 'The Coming Man'. But, like the Labour Party in Britain, the SPD has repeatedly in recent years appeared within sight of victory - and has then fallen behind.
Mr Scharping, prime minister of the Rhineland-Palatinate - Mr Kohl's home region, south of Bonn - comes across as a low-key politician. He shows little natural enthusiasm for pressing the flesh; nor is he seen as a natural orator. But that may not be a disadvantage. Flamboyant politicians are often mistrusted and some argue his managerial style could prove reassuring, in the final run- up to elections on 16 October.
Meanwhile, he looks set today to bring into his campaign team his most important rival in the party - Gerhard Schroder, prime minister of the north-western state of Lower Saxony, who visibly adores the cut-and-thrust of politics and is popular with voters. Since losing to Mr Scharping in the leadership contest last year, Mr Schroder has been sulking in his Lower Saxony tent. Now the new team is expected to include Mr Schroder and Oskar Lafontaine, the fiery prime minister of the Saarland. Mr Schroder shows almost as much self-confidence as Mr Kohl, who is famous for his lack of self-doubt. At the same time, Mr Scharping's cool, almost pedantic approach may reassure those worried by Mr Schroder's pugnacious style.
Mr Scharping can envy Tony Blair, the Labour Party leader. Labour's commanding lead now seems, for the SPD, the stuff of fantasy. For Mr Scharping, one problem is determined by the very nature of the German political system, with the need for consensus between the federal government and the governments of the 16 states, or Lander.
In contrast to the them-and-us political system in the UK, the SPD has been involved in hammering out compromises on all of the most controversial issues in recent years. Mr Scharping admits this makes things difficult in an election year: 'It's a good tradition that questions of great significance are decided by consensus - but that can sometimes give the impression that the difference between the government and the opposition is not so great.'
On one issue at least, the need for European integration, Mr Scharping agrees with Mr Kohl. Fears of a dangerously dominant Germany are, he says, 'totally exaggerated'. In words that could be echoed by Mr Kohl, Mr Scharping argues: 'Sensible German policies will always ensure that the weight of Germany is bound into Europe.'
He is critical of the failure by the Kohl government to do more to curb the upsurge of far-right violence in the past three years. But he distances himself, too, from the vision of a Germany on the edge of an abyss of xenophobia and violence. 'Germany is, as it was, a stable democracy,' he says. 'This is not Weimar.'
The coalition style of German politics means that the arithmetic could throw up many possibilities, after 16 October. The three most obvious are the continuation of the existing coalition between CDU and Free Democrats; a grand coalition of CDU and SPD; or a coalition of Social Democrats and Greens (red-green).
The creation of a minority red- green government in the east German state of Saxony-Anhalt, by grace of the former Communist PDS, aroused controversy, even though Mr Scharping insists that a PDS-tolerated red-green coalition in Bonn is not on the cards.
Mr Scharping says that the issue 'doesn't bother people as much as the CDU would like'. But he also insists that there is a difference between a small regional government, as in Saxony-Anhalt, and the federal government in Bonn. 'International stability', he says, would be affected, if the PDS were to have a say in the creation of the new federal government.
Certainly, Mr Scharping would face a difficult choice - between forming an SPD-led government with the blessing of the PDS, on the one hand, and allowing Mr Kohl to remain as chancellor for the next four years, on the other. Either option would be sharply criticised, by some in the party.
Mr Scharping will consider himself lucky if he gets the chance to lead a government, of any kind. The Social Democrats' hope is that a Scharping-Schroder-Lafontaine team could inject new energy into the campaign. Mr Scharping himself insists: 'There's a growing consciousness that the economic problems have not been solved. And the need for peace and justice in this country is growing, too. Whether it's enough - we'll just have to see, on the evening of election day.'