MUNICH (Germany) - CONSERVATIVES in the southern German state of Bavaria suffered their worst result in half a century in a regional vote on Sunday, dealing a blow to Chancellor Angela Merkel ahead of a 2009 federal election.

Preliminary results showed the Christian Social Union (CSU), Bavarian sister party to Dr Merkel's Christian Democrats (CDU), on 43 per cent, down from 60.7 per cent in the last state vote in 2003 and the party's worst performance since 1954.

Dubbed a 'political earthquake', the result means the CSU will lose the absolute majority it has held in the state assembly for nearly half a century, and in a humiliating setback, be forced to form a coalition with another party.

The sharp fall in support is also a setback for Dr Merkel, who relies heavily on the CSU for power. She now faces a tougher battle to win a second term in a federal vote in Sept 2009.

'This clearly weakens Merkel because her CDU always depends on the strength of the CSU in Bavaria,' said Mr Gerd Langguth, a political scientist at Bonn University and biographer of dr Merkel.

CSU supporters at the state parliament in Munich looked shellshocked and greeted the results with a stony silence.

'This is a painful, difficult day for the CSU,' party leader Erwin Huber said. His counterpart, Bavarian state premier Guenther Beckstein, said the party would have to 'bite the sour apple' and form a ruling coalition.

Both Mr Huber and Mr Beckstein, who took over a year ago from long-time party and state leader Edmund Stoiber, may now be forced to quit, although both said no decisions would be taken until a party meeting on Monday.

Smaller parties
The CSU accounts for more than 20 per cent of the conservative bloc in Germany's lower house of parliament and the Bavarian party's strength helped Merkel win her slim majority in the last federal vote in 2005.

Early results put the centre-left Social Democrats (SPD), with whom Merkel rules in an uneasy 'grand coalition' in Berlin, on 18.6 per cent, weaker than their 2003 showing.

The winners were the smaller parties, including the liberal Free Democrats (FDP), on 7.5 per cent, the Free Voters, on 10.4 per cent, and the Greens, on 9.3 per cent.

After a string of victories in other western states earlier this year, exit polls showed the far-left Left party on 4.7 per cent in Bavaria, short of the 5 per cent threshold needed to make it into the state parliament.

Germany's SPD Foreign Minister Frank-Walter Steinmeier, who will challenge Dr Merkel in next year's federal election called the result a 'political earthquake' for the prosperous southern state known for its annual Oktoberfest beer festival.

The CSU has ruled Bavaria alone for nearly half a century and won over 50 per cent of every vote since 1970.

CSU-led governments have transformed Bavaria from a rural state into a high-tech economy that is home to corporate giants like BMW and Siemens . The state boasts Germany's lowest unemployment and crime rates.

However, analysts say the CSU has suffered from a lack of vision in recent years. Bavarians are also angry about a smoking ban, big spending cuts and heavy losses at state bank BayernLB. -- REUTERS