JAKARTA (Reuters) -Indonesia's ruling party on Wednesday said the running mate of its presidential candidate will be a well-respected, senior cabinet minister, as political heavyweights shore up alliances ahead of a deadline for registering for a 2024 election.

The world's third-largest democracy is set to vote in February to replace President Joko Widodo, or Jokowi as he is commonly known, who has served the maximum two terms allowed.

Ganjar Pranowo, the presidential candidate of the ruling Indonesian Democratic Party-Struggle (PDI-P), will team up with the chief security minister, commonly known as Mahfud MD, said the party's leader, Megawati Sukarnoputri.

"He could be a good referee amid political and business competitions that often feel unfair," she said at a PDI-P event in the capital, Jakarta.

Mahfud, 66, a former chief justice of the Constitutional Court and who political sources say is close to Megawati, is a vocal critic of corruption. His full name is Mohammad Mahfud Mahmodin but he has been known as Mahfud MD for decades.

Jokowi, who is also a member of PDI-P but has a fraught relationship with Megawati, did not attend the party event as he is at a conference in China.

Opinion polls show that Ganjar, a former governor of Central Java province, is neck-and-neck with Defence Minister Prabowo Subianto, 72, who is making a third bid for the presidency after narrowly losing to Jokowi in 2014 and again in 2019.

Prabowo has yet to announce a running mate, but there has been speculation he will pair up with Jokowi's son, Gibran Rakabuming Raka, especially after a top court issued a ruling on eligibility criteria this week that allows the 36-year-old to run in 2024.

The ruling has drawn criticism from the public and raised fears of resurgence of dynastic politics.

Arya Fernandes, an analyst who heads the politics department at the Centre for Strategic and International Studies, said Mahfud would be a boost for Ganjar due to his anti-corruption credentials.

"It's a clever choice," Arya said, adding his background as a member of Indonesia's largest Islamic organisation, Nahdlatul Ulama, would be another electoral advantage.

Several major parties were due to hold meetings on Wednesday, a day before candidates and their running mates are scheduled to register and present their policy platforms to the election commission. Registration closes on Oct. 25.

Ganjar and Mahfud will register on Thursday, house speaker and PDI-P member Puan Maharani said.

Former Jakarta governor Anies Baswedan is also running for president but trailing in opinion polls.

(Reporting by Stanley Widianto and Ananda Teresia; Writing by Kanupriya Kapoor; Editing by Miral Fahmy, Robert Birsel)