German Chancellor Angela Merkel attends the weekly cabinet meeting at the Chancellery in Berlin, Germany, May 10, 2017. REUTERS/Fabrizio Bensch

BERLIN (Reuters) - Chancellor Angela Merkel’s conservatives have pulled ahead of their Social Democrat rivals in the populous western region of North Rhine-Westphalia ahead of a crunch vote in the state on Sunday, an opinion poll showed.

The YouGov survey for broadcaster Sat.1 NRW, published on Thursday, put support for Merkel’s conservative Christian Democratic Union (CDU) at 31 percent in the state, with the Social Democratic Party (SPD) on 30 percent.

Those readings marked a 4 percentage point rise for the CDU from two weeks ago, and a 6 point drop for the SPD.

After suffering humiliating defeats in two other state votes this year, the SPD may have to retain North Rhine-Westphalia (NRW) if its new national leader Martin Schulz is to mount a serious challenge to Merkel’s bid for a fourth term at the helm of Europe’s most populous country and pivotal economy.

Germany votes in a national election on Sept. 24.

Elections in NRW, home to around a third of Germany’s blue chip companies but also the rust-belt Ruhr region, have historically influenced federal politics. In 2005, a crushing defeat for then-Chancellor Gerhard Schroeder’s SPD prompted him to call an early election that he lost to Merkel.

With more than a fifth of Germany’s overall population, the state is now governed by a left-leaning alliance of the SPD and Greens. But an ebbing of support for the environmental party means that coalition is likely to break up.

The YouGov poll put support for the Greens at 7 percent, with the liberal Free Democrats (FDP) and the anti-immigration Alternative for Germany (AfD) both on 9 percent. The far-left Linke was on 8 percent, the anti-establishment Pirates party on 2 percent and ‘others’ on 4 percent.