Leading article: A crucial election that is Ms Merkel's to lose

It had an unpromising and fitful start. The German constitution deliberately makes it difficult for chancellors to choose the time of an election. Gerhard Schröder's decision to "go to the country" after his Social Democratic Party lost regional elections in North Rhine-Westphalia was a choice that would have been natural for a British prime minister in similar circumstances, but raised constitutional questions in Germany. One by one, the legal objections have been cleared. The election campaign has begun.

At first sight, German voters have a clear choice between the past and the future. They have Mr Schröder, the centre-left politician who once saw himself as a German Blair, seeking a third mandate that would give him four more years. And they have Angela Merkel, leader of the centre-right CDU-CSU alliance, and a "new" German in several respects. An East German who grew up under Communism, she is a relative newcomer to politics and, if elected, would be Germany's first female chancellor.

Mr Schröder has a track record, good and not so good, in office. He is an impressive campaigner, convincing on the stump and on television. He is an adept machine politician. Ms Merkel is inferior in every department, except in the one that may make the difference: unencumbered by earlier promises, she can put forward new ideas at a time when Germany sorely needs some.

Over seven years, Mr Schröder has tried to cajole Germans into accepting overdue economic and social reforms. But no sooner had he manoeuvred his most substantial labour reforms past the opposition in the Bundestag than he was punished by his erstwhile voters for moving too far to the free-market right. That was the election in North Rhine-Westphalia which precipitated this general election.

Mr Schröder's dilemma is that this election is being held at a time when voters are still smarting from the new restrictions on their social benefits, but before any economic improvements have had time to work their way through the system. This, though, is politics, and the Chancellor has only himself to blame for the timing of the election. If he had hoped to wrong-foot Ms Merkel, this may be one gamble he will lose. After wobbling initially, her double-digit poll lead is holding steady.

Ms Merkel, meanwhile, has appointed a team of advisers that suggests some radical new thinking, including a rapid shift from direct to indirect taxation. She has to show that what she lacks in experience and charisma, she can make up for in seriousness and innovation. But she also has to convince Germans that her policies present a long-term remedy for their sluggish economy, even if in the short term they are unpalatable.

If this election were a straight duel between these two leaders, the choice would be clear. The presence of several smaller parties, and Germany's system of proportional representation, however, makes the choice, and likely the outcome, more complex. To the natural allies of the major parties - the Greens on the left and the free-market FDP on the right - has now been added the Left party with a traditional left-wing programme.

Mr Schröder has now to fight on two fronts; Ms Merkel has to win well enough to pre-empt a multi-party coalition on the left. As of now, she is well positioned for victory; but the left is not out of the game yet, and a great deal can happen in three weeks.