A result won't be known for two weeks and if no one wins a majority, a second round of voting will take place on April 19.

"If (incumbent) Ahok was to lose, other than politicians using religion as a tool, Islamists will use it to change Islam into Indonesia to their own meaning, that isn't Indonesian," Center for Strategic and International Studies Indonesia researcher Tobias Basuki told CNN.

"They will gain an upper hand. (This) will be the first litmus test."

Rise of conservatism

But with the exception of the severely religious Aceh province, Indonesia is generally a moderate country with a tolerance for other religions and ways of life.

"Indonesia's political Islam is very different from the Middle East -- for example, non-Muslim leaders of a Muslim majority is normal, intermarriage is accepted," Basuki said.

However experts says Indonesia is becoming increasingly conservative, with large anti-LGBT protests in Jakarta and passionate reactions to allegations of blasphemy commonplace in recent years.

Ahok is from two prominent minorities -- he's a Christian and of Chinese ethnicity. Both have been made an issue in the current campaign, Australian National University Bell School of Asia-Pacific Affairs Associate Professor Greg Fealy told CNN.

Fealy said if Ahok loses the election, Indonesian political parties may be less likely to field candidates from the country's ethnic and religious minorities.

"If there was a major position, like Governor of East Java, for a minority, this is too big a risk," he said.

Taking down a president

The fierce campaign to topple Ahok has another target in its sights -- Indonesian President Joko Widodo, also known as Jokowi.

"Before (Joko) the governorship was very boring ... this is the first time Jakarta's seat is considered a stepping stone to the Presidency," Basuki told CNN.

Ahok is a longtime ally of the Indonesian leader, running as Widodo's running mate in the 2012 Jakarta election and assuming governorship after Widodo stepped down.

Whoever beats Ahok for the position would have a high-profile platform from which to challenge Widodo in 2019 -- or be an invaluable ally to whoever does run.

"Jokowi very much wants Ahok to win and he's been trying to back him as much as he could ... he most certainly doesn't want Prabowo's guy to be governor (Anies Baswedan). He could be quite a threat to Jokowi," Fealy said.

Former Indonesian Lieutenant General Prabowo Subianto was Widodo's primary opponent in the 2014 election and is expected to run again in 2019.

"If Jakarta's governor is from the so-called opposition they will impede Widodo's every step, not just in the 2019 election but beyond that," Basuki said.

Jakarta's brash governor

"The second round of the election, I think that will be the really ugly one. What we've seen so far hasn't been pretty but I think there'll be people playing for very high stakes," Fealy said.

"I think it will be much more virulently sectarian and racist."

Ahok's supporters say he is the only choice to lead Jakarta for the next five years.

"I'm very sure those in the grassroots will choose him," Jakarta resident Nyoman Kamajaya told CNN. "Why? Because they're not choosing an imam. They're choosing a leader."

But a large number of people still do not support the Christian Chinese governor, with some saying their religion must be "defended".

"I am Muslim and I will only accept Muslims as my leaders," Jakarta Islamic Center voluneer Suci told CNN.

Whatever the result, Fealy said Ahok will have to bear some of the blame himself for his brash, confrontational style of governing.

"He's a very combative, outspoken, reckless kind of character who has achieved a lot for Jakarta, but he's a character who has created a lot of antipathy towards him," he said.