Updated

Germany's center-left Social Democratic Party is holding a special convention to confirm Martin Schulz as the party's top candidate to challenge Chancellor Angela Merkel in the country's upcoming general election.

Party leaders unexpectedly nominated Schulz after long-time chairman Sigmar Gabriel stepped aside in January. The party has since experienced a surge in the polls not seen in a decade.

Analysts say Schulz benefits from being a relative newcomer to domestic politics. Until his nomination, the 61-year-old was president of the European Parliament.

The Social Democrats' general secretary, Katarina Barley, told reporters ahead of the convention Sunday that the party has seen 13,000 new members join this year.

Merkel, whose center-right Christian union bloc is in a coalition with the Social Democrats, is running for a fourth term on Sept. 24.