* Bavaria holds regional vote one week before federal poll
* Merkel's allies seen restoring absolute majority
* Strong conservative result can boost Merkel, FDP a worry
By Christiaan Hetzner
MUNICH, Sept 15 (Reuters) - Angela Merkel's allies look set to win almost 50 percent of the vote in the rich southern state of Bavaria on Sunday, helping the German chancellor and her conservatives with a show of strength a week before a federal election.
The Christian Social Union (CSU) - sister party of Merkel's Christian Democrats (CDU) - has governed Bavaria for 56 years, styling itself the natural ruler of a state that is proud of its "laptop and lederhosen" economy and traditions.
"Dear Angela, we'll put the ball on the penalty spot, you just have to kick it in," CSU leader Horst Seehofer said.
Polls predict the CSU will get at least 47 percent, allowing it an absolute majority in the regional assembly in Munich and cheering conservatives nationwide. First exit polls are due at 6 p.m. (1600 GMT).
Seehofer wants to put behind him the 2008 election, when the CSU scored its worst result in six decades, 43 percent. That forced it into an alliance with the Free Democrats (FDP), who are also Merkel's coalition partners in Berlin.
The combined CDU/CSU bloc has about 40 percent support nationwide, meaning that if they do win on Sept. 22 they will need a partner to form a government, be it the FDP or the Social Democrats (SPD) with which she ruled in a 'grand coalition' from 2005 to 2009.
In Bavaria and in the Bundestag lower house of parliament, the FDP risks falling short of the 5 percent threshold for a seat in parliament, though their poll results have improved in recent months.
A weak FDP showing in Bavaria might even scare conservatives elsewhere into giving their second vote to the FDP, potentially weakening the share of votes that go to Merkel's CDU.
Bavaria, home to 12.5 million of Germany's 80.5 million people, is the only state with a regional party - the CSU - in the federal parliament.
When other regional conservative parties joined to form the CDU, the CSU remained separate, reflecting Bavaria's strong regional identity. CSU lawmakers make up nearly a quarter of Merkel's conservative bloc.
If Bavaria were a country it would have the euro zone's sixth largest population and economy, which allows it to exert pressure on national policy on issues ranging from energy and the family to the euro zone.
Bavarians consider themselves dedicated Europeans who have benefited from the single currency. Calls within the CSU for Greece to leave the euro zone or to pay its civil servants in drachmas have not prevented it from backing Merkel on bailouts - which one leader likened to "watering flowers in the desert".