Germany's almost 62 million registered voters are being called upon to cast their ballot in Sunday's election, which will decide whether Merkel's center-right coalition will stay in power.

Pre-election polls show the Chancellor's conservative Christian Democratic Union (CDU) 13 percent in front of her nearest rivals, the center-left opposition Social Democrats (SPD) under Peer Steinbrück. However, Merkel's current coalition partners, the pro-business Free Democrats (FDP), have been lagging in the surveys, hovering at the 5 percent threshold for parliamentary representation.

If the CDU, its sister party the Bavarian Christian Social Union (CSU) and the FDP fail to garner the necessary majority to rule, Merkel may be forced into a so-called grand coalition with the SPD, her traditional rivals, as was the case in her first term from 2005 to 2009. The FDP has not only fared badly in surveys, but was also forced to exit the regional assembly in last weekend's state election in Bavaria, achieving a meager 3.3 percent.

The SPD itself favors a coalition with the Greens, but the pro-environment party have not made a good showing in pre-elections surveys, which put them at just nine percent. In 2009, the Greens received 10.7 percent of the vote.

Two new surveys published on Friday put Merkel's existing coalition in a 45-45 percent dead heat with a possible center-left array of SPD, Greens and the Left - although Steinbrück has consistently ruled out a coalition with the latter party, which has received nine percent in recent surveys. The surveys however also showed that up to a third of voters were still undecided.

A new euroskeptic party, the Alternative for Germany (AfD), could also prove a wild card, either by receiving enough votes for parliamentary representation, or by drawing center-right voters away from Merkel's coalition.

"Please go vote"

Both main candidates have now cast their votes.

Angela Merkel went to a polling station at Humboldt University in the central Berlin district of Mitte in the early afternoon to put in her ballot paper, along with her husband Joachim Sauer.

Earlier on in the day, Steinbrück cast his ballot with his wife, Gertrud, in his western home city of Bonn.

Before voting himself, he tweeted: "Today is election day. It's in your hands. Please go vote."

German President Joachim Gauck also voted in Berlin in the morning.

Last campaign pushes

On Saturday, both Merkel and Steinbrück made last attempts to woo voters.

Merkel, 59, told 4,000 of her supporters in the capital, Berlin, that she wanted to continue leading Europe's biggest economy as "your chancellor for another four years."

Amid fresh fears that Germany will end up bearing the major burden in rescuing Greece from its debt woes, she spoke at length about the importance of Europe for Germany.

Germany "can only do well in the long term if all of Europe does well," she said.

"This is why the stabilization of the euro is not just a good thing for Europe but it is also in Germany's fundamental interest," she added.

Visiting Frankfurt on his last campaign day, Steinbrück, 66, told listeners they had the chance to "get rid of the most backward-looking, least capable, most loud-mouthed German government since reunification."

He also answered questions on his calls for a standard minimum wage and his accusations that Germany has seen a widening gap between rich and poor under Merkel. Merkel opposes an across-the-board minimum wage, instead favoring flexible pay agreements negotiated between employers and unions in each respective region and sector.

Steinbrück, who was finance minister in Merkel's 2005-2009 coalition, has had a somewhat gaffe-prone campaign, most lately causing a stir with a picture of him showing a middle finger in reply to a question on his problem-ridden candidacy.

Polls will close at six p.m. local time (1600 UTC), and initial television estimates based on exit polls are expected shortly afterwards. The provisional final results are likely to be confirmed officially by the early hours of Monday morning local time.

Sunday is also seeing elections for the regional assembly in the state of Hesse, where Frankfurt is situated.

tj/jm (AFP, Reuters)