When Jakarta governor Basuki Tjahaja Purnama had some of the capital's sprawling slums levelled this spring, Muslim groups including the hardline "Islamic Defenders Front" (FPI) moved in quickly to help some of the city's poorest residents.
The offer of food, shelter, clothes and money was a lifeline to the struggling families. But religious conservatives, who had long opposed Purnama because he was a Christian, did not stop there.
After a video circulated in October of Purnama, also known as "Ahok", making comments that some Muslims said insulted the Koran, the FPI went into overdrive.
It called for his arrest, bombarded its social media pages with fiery messages and rallied some 150,000 protesters to the streets of the capital earlier this month.
With another mass protest slated for December 2, the FPI has helped trigger a crisis that has engulfed President Joko Widodo, seen as a close ally of Purnama, and damaged the hitherto popular governor's hopes of re-election in a ballot in February.
The FPI, which divides opinion in Indonesia, has also seized the political agenda, using the blasphemy scandal to get people on to the streets and pushing a message of intolerance in a Muslim-dominated country where hardline posturing rarely makes waves.
The FPI said it wants Friday's demonstration to be peaceful, but minorities, including Christians and the lesbian, gay, bisexual and transgender community are fearful of the group.
Around 50 FPI members barged into a Jakarta apartment at the weekend to break up what they said was a gay sex party. The group has vowed to continue to target the LGBT community.
Purnama has been in the Islamists' sights for years.
The FPI believes a Christian, who is also ethnic Chinese, should not hold the powerful position of running the city of 10 million people.
The group, which says it has about five million members, has a history of harassing minorities.
In recent years, they have forced the closure of churches and mosques run by non-Sunni Muslims, raided bars, and caused the cancellation of a 2012 Lady Gaga concert to "protect Indonesians from sin".
When some Jakarta slums were razed in March and April, the FPI encouraged those evicted to form small "pop-up" groups to demonstrate against clearances, Bamukmin said. Some later joined the November 4 protest.
In September, when the case of alleged blasphemy first surfaced, FPI leaders ratcheted up their rhetoric against the governor, calling for his arrest and preaching in mosques that "blasphemy is non-negotiable".
The group also began publishing posts hourly, as opposed to two or three times a day, on Facebook, Twitter and in newsletters to express its outrage.
Their online feeds are now crammed with anti-Purnama traffic, as well as some against Widodo himself, and many posts are being liked, re-posted or commented on thousands of times.
By comparison, the country's biggest moderate Muslim organisation, Nahdlatul Ulama (NU), barely mentions the blasphemy case on its social media pages.