correction: A previous version of this article incorrectly reported that German Chancellor Angela Merkel’s party had dropped 11 percent in the state of Hesse since the previous election. The party’s support fell by 11 percentage points.
BERLIN — Chancellor Angela Merkel’s once-unassailable position in German politics endured yet another blow Sunday as support for her party dropped precipitously in a state that has long been a bellwether for the nation, projected results showed.
The outcome was just the latest indication that Merkel’s grip on power in Europe’s largest economy is slipping, even if there is still no sign of an imminent fall.
The election for the state parliament in Hesse — home of Frankfurt, the heart of German finance — gave Merkel’s center-right Christian Democratic Union (CDU) 27 percent of the vote, according to projections based on partial returns Sunday night.
That was good enough for first place, but down 11 percentage points since the state last voted, in 2013, and represents the party’s worst performance in the state in more than half a century. The party’s state leader, Volker Bouffier, called the outcome “very humbling.”
Backing for Merkel’s coalition partner, the center-left Social Democrats (SPD), also plummeted, falling from 31 percent to 20 percent — a low not seen in 72 years.
After the vote, SPD leader Andrea Nahles called the result “unacceptable” and left open the possibility that her party could bolt from Merkel’s already precarious coalition — a move that would collapse the government.
It remains to be seen, she said, whether the SPD “is still fit for this government.”
As the country’s two traditionally dominant centrist parties flailed in Hesse, forces on either flank surged: the far-right Alternative for Germany (AfD) and the progressive Greens. The latter was vying with the SPD for second place after its best result in the state’s history.
The outcome was an almost exact replay of results in Bavaria two weeks ago, when the CDU’s sister party, the Christian Social Union (CSU), was humiliated in a state where it has long governed without rivals. After that vote, Merkel allies blamed the CSU’s rightward lurch on immigration for its poor results.
But Sunday’s vote suggests the CDU’s image has also taken a strong hit during a year when the nation’s politics have been overshadowed by a sustained feud within Merkel’s government.
The CDU has governed Hesse for nearly 20 years, and the party campaigned on an enviable record in the state of ultralow unemployment, high wages and minimal crime.
But analysts said that voters treated the election as a referendum on the national government, and their reviews were poor.
“The message was very clear: Don’t quarrel. Get together. Be the strong Germany that Europe needs,” said Sigrid Rossteutscher, an analyst at Frankfurt’s Goethe University.
Still, the CDU seemed to have avoided a worst-case scenario in Hesse: the potential humiliation of losing control of the state, as left-leaning parties appeared to have fallen short of the backing needed to form a government on their own. That means the CDU will almost certainly remain in charge, with the Greens and the centrist Free Democrats as likely coalition partners.
A fall from power in Hesse had been seen as a possible prelude to a much more consequential shake-up for the party. The CDU hosts its annual conference in December, and Merkel, who has governed Germany for the past 13 years, will be seeking reelection as party chairwoman.
Had the party relinquished control in Hesse, some analysts saw her as vulnerable to an intraparty challenge. Although the CDU has remained relatively united behind its leader in public, discontent has been building as the party’s fortunes have sunk.
The results in Bavaria and Hesse mirror political trends nationwide. The CDU won a third of the vote in last September’s German election — a historically poor performance for a party that has dominated the country’s postwar politics. But current polls show the CDU not even winning a quarter of the national vote.
The SPD has seen a similarly steep drop nationally, with Germany’s oldest political party falling from second place to fourth, behind the Greens and the AfD.Rossteutscher said the SPD will be reluctant to bring down Merkel’s government because party leaders know that if they do, and early elections are called, the SPD “would be the biggest loser.”
The AfD on Sunday claimed nearly 13 percent of the vote — almost exactly the same percentage that it won in last year’s national elections — and a place in Hesse’s parliament for the first time.
Just five years after the party’s founding as a protest of euro-zone bailouts, the anti-immigrant AfD now controls seats in all 16 of Germany’s state parliaments, in addition to the national Bundestag and the European parliament.
“The election was a success on all fronts,” said the AfD’s leader in Hesse, Jörg Meuthen.
But the night’s biggest winner was the Greens. The party nearly doubled its support from 2013, picking off defectors from both the CDU and the SPD. The result, coupled with a similarly impressive second-place finish in Bavaria, pointed to new vitality on the left of German politics.
“People thought elections can only be won on the far right,” said party co-leader Robert Habeck. But the Greens have proved, he said, that “passion, optimism and pro-European politics can apparently also mobilize support.”
Luisa Beck contributed to this report.