The centre-left opposition party rose to 28 percent in a poll for the Bild am Sonntag newspaper, gaining six percentage points on the previous week to record its best-ever score in the regular survey carried out by the Kantar institute.
Merkel’s centre-right CDU/CSU alliance lost two points, coming in second at 27 percent support.
The centre-left Social Democrats (SPD), Merkel’s junior coalition partners, fell to their worst score since August 2019 with 13 percent.
The Greens’ surge in popularity comes after the party on Monday tapped co-chair Annalena Baerbock, 40, to become its first-ever chancellor candidate.
The nomination of mum-of-two Baerbock, seen as a centrist who advocates a greener economy and a tougher foreign policy stance on Russia and China, has been widely cheered.
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She will also be the only woman in the race to succeed Merkel, who is bowing out after 16 years.
“Germans are in the mood for change,” Bild wrote.
Another opinion poll last Tuesday for broadcasters RTL and NTV was the first to put the Greens in the lead, also giving them 28 percent support.
Merkel’s ruling conservatives have slumped in recent polls as voters punish them for perceived mistakes in the handling of the coronavirus pandemic, corruption scandals and party infighting.
Her bloc unveiled CDU leader and North Rhine-Westphalia state premier Armin Laschet as its chancellor candidate last week, following a bitter power struggle with CSU leader Markus Söder.
But Laschet, billed as the continuity candidate, remains deeply unpopular among Germans.
Observers say there is a realistic chance the CDU/CSU will not re-emerge as Germany’s biggest political force after the September 26th vote.
Bavarian premier Söder, who backed down in the fight for the chancellor candidacy despite strong grassroots support and higher approval ratings than Laschet, said at the weekend he was “not convinced” by Laschet’s candidacy.
The CDU/CSU bloc “needs a fresh start”, he told the Süddeutsche newspaper.