The Social Democratic Party (SPD) has the support of just 21 percent of Germans - the lowest rating recorded for the center-left party in a monthly voter survey conducted for public broadcaster ARD. The SPD's support was at 23 percent in March.

Chancellor Angela Merkel's Christian Democratic Union, which leads Germany's governing "grand coalition" with the SPD and Bavaria's Christian Social Union, also saw voter support drop 2 percentage points to 34 percent.

The Green party enjoyed a 3-percentage-point boost in voter support, bringing the party to 13 percent. Both the Left party and the free-market liberal FDP came in at 7 percent in the April edition of the Deutschlandtrend poll.

Parties look for ways to cope with AfD

Drops for Germany's two largest parties contrast with the ever-increasing backing shown for the Alternative for Germany (AfD), which saw voter support reach a new high of 14 percent in the current survey. A 3-percent increase for the populist, right-wing party comes on the heels of it winning enough votes to enter parliaments in all three states that held elections last month. The AfD is now present in half of Germany's 16 state parliaments but is not represented in the national parliament.

Prior to March 13's election in Rhineland-Palatinate, the state's premier, Malu Dreyer, had been hesitant to meet AfD candidate Uwe Jung for a televised debate, fruitlessly hoping that denying a stage to the AfD would sap its support among the public.

But after the election, in which the AfD placed third with 12.6 percent of the vote, Dreyer said her party - as the state's top vote-getter - would have to find a way of coping with the AfD by focusing on the content of its policy suggestions.

Her diplomatic position, however, wasn't echoed by other lawmakers in other parties - or even everyone in her own.

"We reject cooperation with the AfD," Carsten Pörksen, the SPD's parliamentary leader in Rhineland-Palatinate, said after the election. The FDP in Baden-Württemberg also said it would not cooperate with the AfD. The southern German state also held elections in March and saw AfD place third at 15.1 percent.

But ignoring the elected AfD lawmakers, as is also done in some of the states where the party is already represented, isn't the best course of action, according to Werner Patzelt, a political scientist at the Technical University of Dresden.

Instead of potentially creating political martyrs out of AfD lawmakers, he told the German news agency dpa, other parties should challenge the party's positions.

"Whoever wants to support the AfD only needs to give it space and not confront it on the issues," Patzelt said. "Heated debate is the right way to deal with AfD positions."