Jakarta's Christian governor Ahok, or Basuki Tjahaja Purnama, led the polls by a slim margin a few days ahead of the runoff election.

A survey conducted by Charta Politika from April 7 to 12 showed that Ahok and his running mate Djarot Saiful Hidayat were leading by 47.3 percent, while Ahok's rival Anies Baswedan and his running mate Sandiaga Uno were second place at 44.8 percent, according to CNN Indonesia.

The survey, which involved a total of 782 respondents from various parts of Jakarta, was carried out using a multi-stage random sampling method. It had a 95 percent confidence level and a 3.5 percent margin of error.

Another survey conducted by the National Media Survey (Median) from April 13 to 14 also placed Ahok and Djarot at the top with 49 percent, followed by Anies and Sandiaga at 47.1 percent, according to local media outlet TribunNews.

However, another survey from Indikator Politik Indonesia put the Anies-Sandiaga tandem on first place at 48.2 percent and the Ahok-Djarot tandem on second place at 47.4 percent.

Experts say the gap between the two sets of contenders is too close, making it difficult to predict who would emerge the winner.

An earlier survey conducted by Saiful Mujani Research and Consulting (SMRC) between March 31 and April 5 showed Anies leading the race with 47.9 percent and Ahok a close second with 46.9 percent.

"The gap between them is too narrow, so we cannot say that Anies is leading," Deni Irfani, researcher at SMRC, said, according to VOA News.

Interestingly, in the SMRC survey, 32.4 percent of the respondents who said they will vote for Anies gave religion as their primary reason for choosing him, while more than 40 percent of those who said they will vote for Ahok said they will choose him because of his track record as governor.

On Feb. 15, Ahok won the Jakarta gubernatorial elections. However, because he was not able to secure 50 percent of the votes and only got 42 percent, another round of elections will be held on Wednesday. With Agus Harimurti Yudhoyono out of the picture, it is expected to be a tight race between Ahok and Anies.

Last year, Ahok was the leading contender for the gubernatorial seat because many people were satisfied with his performance as governor. However, he got caught in a controversy involving issues of religion, which affected his chances of winning.

A group of Muslim hardliners had been campaigning against him and telling the people that Muslims should only vote for Muslims. Ahok is a Christian with an ethnic Chinese background.

In one of Ahok's speeches, he was recorded as quoting a Quranic verse, which his critics used to accuse him of blasphemy. Reports said the video was highly edited to make it look like he was saying something negative. The blasphemy allegations gave rise to massive rallies led by Muslim extremists calling for his arrest.

Ahok is presently on trial for blasphemy, but the trial was suspended to give way for the runoff election. Many say the election is a test of religious tolerance for Indonesia, where freedom of religion is legal.

The Indonesia National Police will deploy 60,000 police officers on Wednesday to ensure Jakarta's security.  

"I have coordinated with the TNI Commander and the Minister for Political, Legal, and Security Affairs, in order to mobilize backup personnel if needed," police chief General Tito Karnavian said.