When Joko Widodo, the incumbent presidentof Indonesia, last year chose Maruf Amin as his running mate for the general election this April, it became clear that Indonesian politicsis now backedinto a corner. Mr. Maruf is an Islamic cleric and scholar, and Mr. Joko was perhaps hoping to dampen attacks from conservative and radical Islamic groupsthathave called him anti-Islam (even though he is Muslim himself). Instead, he has built a Trojan horse for his opponents outside the walls of his own city.

The presidential race, in which Mr. Joko is again facingPrabowo Subianto, aex-army general and former son-in-law ofthe dictator Suharto, looks like a replay of the 2014 contest. Back then, Mr. Joko won by a small margin, on a platform promisinga grand maritime strategyfor Indonesia and to revitalize the economy partly through major infrastructure projects. This year, it seems, the decisive issue will be the candidates professed commitment to Islam.

Mr. Joko and Mr. Prabowo are scheduled to meet for their second debate on Feb. 17, and the agenda will focus on natural resources, infrastructure and the environment. But soon enough, the main issue of this election religion will return to the fore.

In the last four years, Mr. Joko has offered a modicum of hope to progressive and pro-democratic groups. He is not an ideal figure and has been slow in dealing with human rights issues like military violence against civilians. But there is no other choice. With opposition parties the Great Indonesia Movement Party, the National Mandate Party (PAN), the Prosperous Justice Party increasingly supported by conservatives and radicals, including some who wish for the Suharto familys return to power,anyhope for a more democratic society has been placed on Mr. Jokos shoulders.

Polarization has deepened since Jakartas gubernatorial election two years ago. Mr. Joko supported the incumbent Basuki Tjahaja Purnama against Anies Baswedan, a former education minister of Arab descent. Mr. Basuki, being of Chinese and Christian heritage, became an easy target for a campaign based on ethnic and religious differences. Mr. Basuki wasnt just defeated in the election; Mr. Aniess supporters also succeeded in sending Mr. Basuki to prison on charges of blasphemy against Islam. (He wasreleased only last month.)

Mr. Prabowo and the rest of the opposition evidently learned a lot from Mr. Basukis downfall.In 2014, they ran an antiquated campaign based on the supposed resurgence of communism and the Indonesian Communist Party, and failed. The Jakarta election has taught them that tapping Muslim values is an effective way togalvanizepopular support.

Rally Alumni 212, one of the movements behind the campaign that put Mr. Basuki in jail, and the Islamic Defenders Front, an Islamist pressure group that sometimes acts as a sort of Islamic morality police, held the forum of Islamic scholars that recommended Mr. Prabowo asapresidential candidate. But these religious conservatives dont much care that Mr. Prabowo doesnt actually have a strong Muslim background: We are pretty laid back about religion, he has said, referring to his multidenominational family.They care that he is the only viable competition to Mr. Joko and that he welcomes their support.

The strategy of attacking Mr. Joko by manipulating religious sentimenthas begunin earnest. Unlike Mr. Basuki, he is Muslim but that doesnt mean religion cant be used against him, too. The harshest accusation he has faced so far is that his policies are anti-Islam or against the ulema, Muslim scholars.

Here is one example of that, supposedly: The Joko governments decision todissolve Hizbut Tahrir Indonesia, a pan-Islamist political organization that supports the creation of a worldwide caliphate. Another purported sign of the governments anti-Islam bend is a subpoena that was issued two years ago against Rizieq Shihab, an imam from the Islamic Defenders Front, whom the police suspected ofsexting and violating anti-pornography laws.

The voices of Islamic groups have seemed amplified of late, but, to be honest, they have been sounding for quite a long time, both in politics and throughout society. The 1998 Reformasi movement, which ended Suhartos 32-year dictatorship and brought democratization, didnt just allow for political liberalization; it also opened up a space for Islamic political ideas.

The Prosperous Justice Party, formerly known as the Justice Party, was born from on-campus spiritual groups, but it now openly promotes the application of Islamic law.PAN,at first an inclusive nationalist party, has moved closer to conservative Islamist groups. Amien Rais, one of PANs founders, doesnt hesitate to call it the party of Allah and to call Mr. Jokos Indonesian Democratic Party of Struggle the devils party.

In the late 1990s, when you went to a public school, you rarely came across a female student or teacher who was wearing a head scarf; today, its the opposite. Same for employees in government offices. Of course, this doesnt mean that these women necessarily support the political opposition, and it cant be assumed that they are conservative, much less radical. The head scarf might be a simple expression of individual piety. Still, the trend cant be ignored either.

Regional ordinances to accommodate Shariah law have multiplied, the result of the relative autonomy of some regions. The specifics vary, ranging from the call for city officials to wear Muslim dress to the ban on the sale, distribution and consumption of alcohol. More absurd and more frightening are the movements for underage marriage and against vaccines. Both are quite shrill, and both use religious explanations to justify their stances:Early marriage prevents adultery, the popular cleric Ustaz Arifin Ilham has said, and according to one fatwa,vaccines are not halal. Idioms like hijrah meaning to improve ones life by conforming to Islam are heard more and more frequently.

With the Islamization of Indonesian society now evidently being mobilized toward political ends, Mr. Joko must proceed with caution.Yet he may have gone too far.

To give a good impression to Muslim voters, Mr. Joko has been presenting himself as a pious leader who worships diligently. He has even becomea prayer imamand makes frequent visits to Islamic boarding schools. He has also closed his eyes and ears to certain cases brought on religious grounds, knowing that any statement could inflame grass-roots Muslims.

Mr. Joko didnt stand up for Mr. Basuki when he was tried and then imprisoned.He chose to stay silent when a woman in Medan, in northern Sumatra, was charged with blasphemy for complaining about the volume of the call to prayer. Nor did he make any comment in a case involving the forced removal of a cross-shaped headstone from a cemetery in Yogyakarta, in central Java. Last month,Mr. Jokoeven consideredgranting an early release from prison to the radical cleric Abu Bakar Bashir, who was convicted of terrorism. (Mr. Bashir wasnt freed in the end because herefused to pledge allegiance to the state.)

Mr. Joko should be upholdingmoderate politicsby standing up to the opposition, conservatives and radicals who seek to manipulate religious sentiment; thats what his supporters are hoping from him. Instead, he has agreed to walk across a tightrope held up by his political rivals. This has culminated in his choice of Mr. Maruf for running mate who just as easily could have run with the opposition.

Mr. Maruf heads the Indonesia Ulema Council, the national clerical body that issued the fatwa calling Mr. Basuki a blasphemer, and he gave incriminating testimony against Mr. Basuki in court. He isnt just conservative; he is intolerant. He forbids the exchange of Christmas greetings. He rejects theAhmadiyya, an alternative Islamic sect. He condemns L.G.B.T. activities. He wants to limit houses of worship for non-Muslims.

Mr. Joko might remain in power, but we dont have to wait until April to find out the real outcome of this race. No matter who ends up being president, conservative Islamic groups, backed by radical groups, will win have already won the election.

Eka Kurniawan is the author of Vengeance Is Mine, All Others Pay Cash, Beauty is a Wound and Man Tiger. This essay was translated from the Bahasa Indonesia by Annie Tucker.

**P.S.**The US Presidential election is almost two years away. Yet our mainstream media carries wall to wall news accounts of US politics and Democratic Primaries. At the moment, a very important election is pending in Indonesia but our media scarcely mention it.