(Bloomberg) -- Voters in Indonesia’s capital choose its next governor Wednesday in an early test for President Prabowo Subianto after he took office last month.

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The election pits Prabowo’s candidate, former West Java Governor Ridwan Kamil, against the opposition pick, former cabinet secretary Pramono Anung, for control of a metropolis that accounts for about a fifth of the country’s economic output.

Whoever wins will face a range of challenges including traffic congestion, pollution and the fact that the city of more than 11 million people is sinking. The new governor may even preside over a defining moment in Jakarta’s history, when it relinquishes its duties as Indonesia’s seat of government to a new city being built in the rainforests of Borneo more than 1,200 kilometers (750 miles) away.

The role is a career-maker in Indonesia, a stepping stone to becoming the president of the archipelago that spans three time zones and more than 17,000 islands.

The race remains wide open. The latest opinion poll showed Ridwan falling behind Pramono for the first time, but about a quarter of voters have yet to decide who they’ll choose.

A run-off is likely, with neither of the top two candidates set to get more than 50% of the vote. Initial results are expected from 3 p.m.

The Jakarta contest is the most prominent of local elections taking place in 37 provinces across Indonesia.

It’s also one of the first chances for voters to register their level of support for Prabowo after he became Indonesia’s eighth president in late October following a landslide victory in a February election. Prabowo, who’s allied with his predecessor, Joko Widodo, is seeking to further consolidate power after forming a coalition government that controls some 80% of national parliament seats.

The former general has set out ambitious targets ranging from achieving 8% annual growth in the next few years to carrying out a $30 billion free lunch program for schoolchildren.

Controlling the island of Java, which counts Jakarta as its biggest city, is key to the success of those policies since more than half the country’s population lives there.

If Prabowo’s candidates lose in Jakarta and Central Java, investors may sell Indonesian stocks, according to Lionel Priyadi, a macro strategist at Mega Capital Indonesia, a brokerage based in Jakarta.