JAKARTA (Reuters) - A small, influential Islamist party in Indonesia is alarming moderates who fear this secular but predominantly Muslim country may head for wider use of sharia law and become less tolerant of other religions and cultures.
The sprawling Southeast Asian archipelago, home to the largest Muslim population in the world as well as to substantial Christian, Hindu, and Buddhist minorities, has enshrined religious freedom in its constitution.
But with the rising influence of the PKS party, some moderates fear Indonesia will tilt towards more conservative Islamic and nationalist policies such as Islamic laws requiring women to wear hijabs and permitting polygamy, curbs on minority religions, and perhaps a cooler welcome for foreign investors.
"You can forget about the 1945 Constitution, which guarantees freedom for all kinds of minorities," said former president Abdurrahman Wahid, who remains influential in Indonesia's biggest Muslim organization, Nahdlatul Ulama or NU.
"They would try to enact Islamic law," he said, referring to the Prosperous Justice Party (PKS), an Islamist party which draws inspiration from Egypt's banned Islamist party the Muslim Brotherhood.
Already, President Susilo Bambang Yudhoyono, a reformist ex-general who depends on a coalition including Islamist parties, has bowed to pressure from militant Muslims by ordering restrictions on a controversial Islamic sect last month.
In the decade since former president Suharto's ouster, which ended 32 years of autocratic rule, democracy has flourished.
Indonesia has new political parties, direct elections for the president and local leaders, and greater freedom of speech, including a wide range of moderate and extremist religious views.
Among the new parties was the PKS, which has won a string of recent local polls, rattling established rivals such as Golkar, Suharto's political machine, and PDI-P, headed by former President Megawati Sukarnoputri.
Now the PKS aims to increase its political clout by winning a fifth of the votes in next year's elections so it can take a stab at the presidency, to the alarm of moderates. In Indonesia, parties with a strong showing in the parliamentary election can field a candidate in the presidential ballot.
Some moderates see the PKS as a non-violent, Indonesian version of Palestinian Hamas. Both were inspired by the Muslim Brotherhood, and its founder Hassan al-Banna, and owe much of their success to the fact they focus on non-corrupt government and an effective network to win grassroots support.
Promising "clean, caring and professional" government, the PKS has wooed ordinary Indonesians frustrated by widespread graft and the lack of jobs. It has also won respect by responding quickly to disasters, such as the tsunami in Aceh, with offers of medicines, food and money.
"The political map of Indonesia, it's changed," said Tifatul Sembiring, PKS chairman.
The PKS won 7.3 percent of the vote in the 2004 general election, earning a handful of cabinet posts. Now the party wants to shake off its Islamist reputation and has adopted a more pluralist approach in order to win 20 percent in 2009.
"We want to try to change our image," Sembiring, dressed in a suit and tie, said at his modest office in south Jakarta.
Key to the PKS's success is its efficient network of cadres. At the end of last year it had 722,000 activists, many of whom spread the word during weekly study sessions, or tarbiyah, and go door-to-door to recruit new members.
"Tarbiyah is a program of political education," said Sembiring, a computer sciences graduate who studied international politics in Islamabad.
Classes cover the main topics of Islam -- God, the prophet, and Islamic regulations -- and are compulsory for all cadres, regardless of rank, he said.
"It's like a hierarchy. I give the command ... and the person will distribute this. We have no media, like TV, radio, newspaper. But we try to create this system, and it's effective."
Leaders of Indonesia's two biggest Muslim groups, NU and Muhammadiyah, as well as rival political parties, are alarmed by the PKS and its effectiveness as a grassroots organization.
Haedar Nashir, vice chairman of Muhammadiyah, has accused the PKS of infiltrating his organization, and has warned that a PKS takeover would destroy Muhammadiyah and Indonesia because the PKS does not separate politics from religion. Muhammadiyah also issued a decree formally banning the PKS from its ranks.
"Of course we will influence all the people, even Muhammadiyah, even NU. We want to get more support from the people," said Sembiring.
Vice President Jusuf Kalla, chairman of the mainstream Golkar party, said he doubts the PKS will be a threat in the 2009 poll.
"They meet regularly. Not only in the mosque. Mostly outside, working on social problems, education, health. They will have good growth, but in my opinion they cannot reach a large number," said Kalla.
"PKS is a very disciplined party. Their ideology is Muslim ideology," while their organization is based on political cells, added Kalla.
Earlier this year, the PKS romped home with the governorship of West Java, the biggest province by population, and of North Sumatra. It came a close second in last year's race for governor of Jakarta, with 42.5 percent of the vote, despite fears it might introduce sharia-style laws and curb the capital's nightlife.
A recent survey showed 6 percent of those polled supported PKS, while 17 percent chose PDI-P and 15 percent picked Golkar.
A separate presidential poll showed that PKS founder Hidayat Nurwahid, who is Javanese, would get 5 percent of the vote, while Sukarnoputri would get 30 percent and Yudhoyono 21 percent.
With several months still to go, the PKS "probably have the potential to increase" their share of the vote," said Saiful Mujani, of political polling agency Indonesia Survey Institute.
"Don't forget that PKS voters are young, educated voters who serve as socialisation agents with good skills in mass mobilization. They are skilled, determined, and ideological. That ideological element is hard to find in other parties."
Editing by Megan Goldin