Chancellor Angela Merkel's center-right coalition was in a dead heat against the combined leftist opposition in an opinion poll by the Allensbach institute that was released ahead of the election, according to Reuters.

The Allensbach poll also showed support for the eurosceptic Alternative for Germany (AfD) party at 4.5 percent, or just below the 5 percent threshold needed to win seats in parliament, one point up from its last poll on Sept 18.

The Allensbach poll found Merkel's conservatives rising to 39.5 percent from 39 percent since September 18 while their coalition partners, the Free Democrats (FDP), slipped half a point to 5.5 percent for a combined 45 percent.

The main opposition Social Democrats (SPD) were up 1 point to 27 percent while their allies, the environmentalist Greens, were down 2 points to 9 percent. The hardline Left party was unchanged at 9 percent in the Allensbach poll.

Other polls this week point to a tight result on Sunday, Sept 22, increasing the likelihood of a Merkel-led right-left "grand coalition" government.

"Germany remains committed to euro zone membership, but public opinion and institutional constraints ... limit the scope for any German government to drastically alter course towards more generous support policies," analysts at Citi Research said in a research note.

Merkel, 59, would be only the third post-war German leader, after Helmut Kohl and Konrad Adenauer, to win three terms. After Jean-Claude Juncker of Luxembourg and Andrus Ansip of Estonia, she is Europe's longest-serving leader.