Former Jakarta Governor Anies Baswedan has named the chairman of Indonesia's largest Islamic party as his running mate for the 2024 presidential election, a move aimed at boosting his popularity in the Muslim-majority country.

Opinion polls have forecast the election to be a close race between Central Java Governor Ganjar Pranowo and Defence Minister Prabowo Subianto, who have both received the support of the current president, Joko Widodo.

Anies, however, has been falling behind.

Anies' vice presidential pick, Muhaimin Iskandar, leads the National Awakening Party (PKB), which has strong ties with Indonesia's biggest Islamic organisation, Nahdlatul Ulama (NU), which boasts 40 million members.

Prabowo and Ganjar have yet to name their vice president choices. Candidates are expected to formally register between October and November.

"With PKB joining, it feels like this coalition will move faster, be bigger and more stable," Anies said in a rally broadcast from the city of Surabaya, East Java.

Coalition dynamics

Running with Muhaimin could broaden Anies' appeal to voters, as PKB and NU are seen as promoters of moderate Islam, said political analyst Djayadi Hanan, adding that Anies needed "a breakthrough" as his base voters were mostly conservatives.

Choosing Muhaimin could, however, harm Anies' chances after former President Susilo Bambang Yudhoyono and his party withdrew from Anies' coalition on Friday, accusing him of backpedalling on a promise to choose Yudhoyono's son as his running mate.

"If you cannot be trusted now, cannot keep commitments, what will you do when you hold great power?" the former president said.

The decision could also hurt the campaign of Defence Minister Prabowo. Muhaimin had previously pledged to support the controversial ex-special forces general in 2024.

Sufmi Dasco Ahmad, a senior member of Prabowo's Gerindra party, said the announcement "automatically ended the political cooperation of Gerindra and PKB" but added his party respected Muhaimin's decision.