BERLIN (Reuters) - German Chancellor Angela Merkel’s conservatives have extended their lead over the center-left Social Democrats (SPD) to 12 percentage points, a poll showed on Wednesday, almost four months before a federal election.

Armin Laschet, top candidate of conservative Christian Democratic Union (CDU) in North Rhine-Westphalia and German Chancellor Angela Merkel attend an election rally in Aachen, Germany, May 13, 2017. REUTERS/Thilo Schmuelgen

The Forsa poll for the weekly magazine Stern and broadcaster RTL put Merkel’s Christian Democrats (CDU) and their Christian Social Union (CSU) Bavarian sister party on 38 percent, up from 36 percent a week ago. The SPD fell three points to 26 percent.

Forsa carried out the poll before an important state election on Sunday won by the CDU.

Other polls have put the conservatives about 9-10 percentage points ahead of the SPD nationally.

The latest Forsa poll adds to expectations that the conservatives will win the Sept. 24 federal vote. Merkel, first elected in 2005, will be seeking a fourth term.

The conservatives upset the governing SPD in an election on Sunday in North Rhine-Westphalia, Germany’s most populous state and a longtime SPD stronghold that is seen as an indicator of the national electoral mood.

The Forsa poll put the liberal Free Democrats (FDP), the conservatives’ preferred coalition partner, on 8 percent, giving the two groups 46 percent altogether.

The SPD, environmentalist Greens (7 percent) and the hard-left Die Linke (8 percent) together have 41 percent.

The nationalist Alternative for Germany (AfD) party, which has no political allies, is on 7 percent.

The poll was conducted May 8-12, included 2,506 respondents and had a margin of error of +/- 2.5 percent.