Angela Merkel's long-term future as Germany's first conservative female leader is on a knife-edge; the country votes today in a general election that is destined to make or break her political career.

The popular 54-year-old chancellor has effectively staked her future on being able to abandon her "grand coalition" government with the Social Democrats and form a new alliance with the pro-business Free Democrats.

Opinion polls failed to predict a decisive outcome of today's vote. The question remains whether Merkel will pull off her plans or be forced to carry on with the unstable grand coalition that could collapse at any time and end her career.

Some polls suggested, by a margin of 1%, that Merkel would be able to abandon her current coalition. Others forecast that she would fail to do so by a similarly small percentage. Adding to the almost complete unpredictability of the outcome, 40% of Germans are still undecided.

Commentators said the election placed Germany at a crossroads. A liberal conservative coalition, commonly known as black-yellow, would allow Merkel to head a government that would pursue the programme of tax cuts and liberal market reforms that she had promised to implement in the run up to Germany's 2005 elections, before she was forced to co-habit. It would also guarantee a continuation of Germany's commitment to providing a military presence in Afghanistan

But in any new grand coalition, the Social Democrats, who are already suffering the biggest drop in popularity on record, would be under pressure from within to abandon the alliance with Merkel's Christian Democrats and join forces with the new-look communist party, the Linke, as it has done in several regional parliaments. Such a move would inevitably force new elections and could result in a coalition of Social Democrats, the Linke and the Greens governing Germany. It would also mean the end of Merkel's career.

"Another grand coalition could break up at any moment," Margaret Heckel, a political commentator and author of a best-selling book on the German leader, said yesterday.

"The chancellor would be unlikely to survive in that case; she would have twice failed to emerge as a clear victor." In 2005, Merkel secured only a wafer- thin majority.