* Data shows "same religion" most common reason for vote
* Voters from President's coalition partners rejected his ally
* Coalition allies didn't mobilize vote for Widodo's ally
* Widodo popular but political Islam seen factor in 2019 election (Adds implications for 2019 presidential race)
By Tom Allard
JAKARTA, April 21 (Reuters) - A polarising election for Jakarta governor saw Islamic identity politics come to the fore and exposed fractures in Indonesian president Joko Widodo's fragile ruling coalition, an exit poll has revealed.
Widodo's political ally Basuki Tjahaja Purnama, the ethnic Chinese Christian incumbent, was resoundingly defeated by Muslim rival Anies Baswedan in a vote seen as a litmus test of the secular traditions of the world's largest Muslim-majority country.
Unpublished data from an exit poll by Litbang Kompas, which Reuters reviewed, found "same religion" was by far the most common reason why voters supported the victor.
Just under 34 per cent of the 1,289 respondents surveyed at 400 polling stations across the Indonesian capital cited religion as the primary reason for backing Baswedan, followed by 14.9 per cent who cited "being with the common people".
"The biggest share of Anies supporters based their choice on similarity in religion and ethnicity," said Bestian Nainggolan, a researcher at Litbang Kompas, a leading pollster. "Programmes and performance were not a dominant consideration."
The exit poll also showed voters who were allied to political parties in Widodo's unwieldy parliamentary coalition, often rejected Purnama - a key ally of the president.
The trends in the Jakarta race are being closely scrutinized for pointers in the next presidential election in 2019, when Prabowo Subianto, who backed Baswedan, may again challenge President Widodo. Subianto lost the 2014 contest to Widodo.
Before he won the presidency in 2014, Widodo was the governor in Jakarta and Purnama his deputy.
Widodo, the first Indonesian leader to come from outside the political and military establishment, relies on an unstable coalition of parties in parliament needed to pass his reform programme.
DIDN'T MOBILIZE VOTERS
Supporters of the United Development Party (PPP) and the National Awakening Party (PKB), two Islamic parties in Widodo's coalition, mostly voted for Baswedan - despite the parties formal backing for the incumbent governor.
Just 29 per cent of PKB supporters, and 11 per cent of PPP loyalists, supported Purnama, known by his nickname Ahok.
"It's hard to know if the leaders of these two parties were serious about supporting Ahok or they just wanted the money, the funding for the campaign," said Ade Armando, a researcher at SMRC.
"They did not do a lot to mobilise their supporters."
More worrying still for the president were the voting patterns of supporters of two bigger parties in his coalition - Hanura and Golkar - that also supposedly backed Purnama.
Just 38 per cent of supporters of Hanura, the party of Widodo's co-ordinating minister for security Wiranto, backed Purnama, the poll found. Six out of 10 supporters of Golkar, the party of Vice President Jusuf Kalla, voted for him.
Golkar, the party created by former authoritarian president Suharto, is Indonesia's second largest.
As a delighted Baswedan declared victory on Wednesday, he was flanked by Aburizal Bakrie, a former Golkar chairman. Also with him was Erwin Aksa, another Golkar figure and Kalla's nephew.
NO VOTE FOR NON-MUSLIM
A blunt-talking reformer, Purnama enjoyed soaring public approval as governor for policies targeting infrastructure, flood mitigation, waste management and corruption eradication in Indonesia's teeming, clogged capital.
That support - at least when it came to voting intentions - dramatically reversed in October after Purnama was accused of insulting a passage of the Koran interpreted by some as prohibiting Muslims from voting for those of other faiths.
Amid large, well-funded rallies in November and December, where hundreds of thousands of protesters heard calls for his imprisonment, Purnama - widely known by his nickname Ahok - was put on trial for blasphemy.
A little over a week ago, pollster SMRC found 76 per cent approved of Purnama's performance as governor, while 48 per cent said they would vote for him.
The divide between Purnama's performance rating as governor and voter approval could be explained by the potency of the message that Muslims could not support a Christian candidate, SMRC's Armando said.
While the Jakarta election points to the rising influence of conservative Islam in Indonesian politics, and his ally defeated under extraordinary circumstances, Widodo remains personally popular.
"The vote (Wednesday) was not a rejection of him or his policies — rather, other factors were at play," political risk consultancy Eurasia Group said in a research note.
(Reporting by Tom Allard; Editing by Bill Tarrant)
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