Germany’s center-left Social Democratic Party has claimed victory in the country’s general elections, with preliminary results showing the SDP defeating the center-right Union (an alliance of the Christian Democratic Union and the Christian Social Union), likely spelling the end of 16 years of Union control.

Sunday’s election, Germany’s first without Chancellor Angela Merkel on the ticket, gave Merkel’s Union its worst showing in the post-World War II era. The CDU and CSU are currently projected to receive just 196 seats in the Bundestag, with a total of 24.1% of the vote. The incoming Bundestag is estimated to have between 735 to 740 members.

In 2017, the Union received a total of 32.9% of the vote, receiving 246 seats. Failing to secure enough for an outright majority, the Union formed a broad unity government with the SPD.

The SDP is estimated to have won 206 seats, with 25.7% of the vote, up from 20.5% of the vote and 153 seats in 2017.

Social Democrats claimed victory Monday, saying the results amounted to a mandate for the party to lead the next government.

The Green Party also saw major gains in Sunday’s election, and is expected to rise from 67 seats in the 2017 election to 118, after surging from 8.9% of the vote four years ago to 14.8%.

The center-right, classical-liberal Free Democratic Party (FDP) made marginal gains, rising from 80 seats to 92, while the nationalist Alternative for Germany (AfD) fell from 94 seats to 83, dropping from 12.6% of the vote in 2017 to 12.6% Sunday.

The Left Party (Die Linke) also lost ground, plummeting from 69 seats in 2017 to 39, after its vote share fell from 9.2% four years ago to 4.9%.

While the Social Democratic Party is expected to begin efforts soon to try to form a new coalition, a new government could take weeks or even months to be formed, given the SDP’s razor-thin margin over the Union, and the difficulties in forming a workable coalition.