Pollster Infratest dimap delivered alarming trends for Germany's long-established parties on Wednesday. A new survey showed further erosion in voter support for the governing coalition partners. The results were especially bitter for the center-left Social Democrats (SPD), Merkel's junior partners at federal level.

The SPD, which peaked in 2005 at 35 percent, slumped to just 20 percent in Infratest's sampling of 1,503 voters, conducted on Monday and Tuesday, for the public ARD television network's channel WDR.

It is the SPD's lowest level of support since 1997 in regular "DeutschlandTrend" surveys, usually conducted for the ARD on Sundays.

AfD supporters undeterred by anti-Islam agenda

The 15 percent for the AfD followed its weekend conference in Stuttgart where the populist party adopted an anti-Islam manifesto.

It's anti-immigration platform prompted widespread condemnation by established parties facing a new upstart third-placed party in Germany's political scene.

The 33 percent overall for Merkel's bloc, comprising her Christian Democrats (CDU) and allied Bavarian Christian Social Union (CSU), ranks as the conservative's lowest rating since October 2011 in trends regularly measured by pollsters for the ARD network.

Alarming returns for SPD's Gabriel

Also alarming was the personal rating for SPD leader Sigmar Gabriel (pictured above, second from left): Only 38 percent of voters support the German vice-chancellor, SPD chairman and would-be aspirant to lead the SPD into next year's federal parliamentary election.

His party colleague, Foreign Minister Frank-Walter Steinmeier (pictured above, left) topped the list of Germany's favorite politicians, with 70 percent voter support, followed by conservative veteran Finance Minister Wolfgang Schäuble on 60 percent.

Merkel came third in the personality stakes, scoring 55 percent, a decline of 1 percentage point since the previous survey. Fourth was Greens' co-leader Cem Özdemir.

EU-Turkey deal unpopular

Ask about the recent EU-Turkey deal, only 33 percent of those surveyed said they favored visa-free entry to Europe for Turkish citizens. Only 38 percent endorsed the deal, designed to redistribute asylum-seekers stuck in Greece across the European Union.

The CDU/CSU bloc, commonly known as the "Union," once garnered well over 40 percent. Such results came most recently during 2005 and again around 2014, according data from six various pollsters collated in a chart maintained by the news magazine "Der Spiegel."

Asked if they were satisfied or very satisfied with the work of Merkel's coalition, 46 percent answered yes, down 2 percentage points.

Support for Greens, Left unchanged

Two other established parties held their ground: Support for the Greens remained unchanged at 13 percent, according to Infratest-dimap. The ex-Communist Left party climbed to 8 percent, up one percent.

The Greens' rating follows Monday's finalization of a regional coalition in Germany's southwestern state of Baden-Württemberg, to be led for a second term by its charismatic Green's Premier Winfried Kretschmann.

That coalition amounts to a relegation to junior partner for Merkel's CDU, which until 2011 had governed Baden-Württemberg for decades.

Trailing on 6 percent nationwide and just above a 5 percent threshold for parliamentary entry is the liberal Free Democrat (DP) party, down one percentage point.

Germany's 2013 federal election left the liberals without seats in the federal Bundestag parliament. In recent regional elections, it made several comebacks, for example, in the state of Rhineland-Palatinate.