Others say it is not Islam, but fear of being branded a US stooge that has kept politicians quiet on the subject of terrorism.
Muslim parties could also play a key role in deciding who wins Indonesia's presidential election in July, as no candidate is expected to triumph without support from other parties.
Another factor keeping voters away from the Islamists is that the two big secular-nationalist parties, President Megawati Sukarnoputri's Indonesia Democratic Party-Struggle and Suharto's former ruling vehicle Golkar, have taken Islam more seriously.
In Megawati's party, surveys show growing numbers of members are pious Muslims, said Robert Hefner, an author on Indonesian Islam at Boston University. As for Golkar, its leadership is increasingly filled by Muslim intellectuals.
"There are some basic cultural changes that these [two] parties have responded to, tapping Islamic sentiment while steering clear of the hot-button issues, namely Sharia and the establishment of an Islamic state," Hefner said.
Besides the Prosperous Justice Party, the United Development Party of Vice President Hamzah Haz and the Crescent Star Party are the most identifiable Islamist parties in Indonesia. All eschew the violence of the fringe militant groups.
Such conservative Islamist agendas were banned under Suharto, and to many Indonesians, hold little sway today.
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