One of the biggest surprises for the Bush administration in postwar Iraq has been the rise of Shia religious power.

In southern cities and Baghdad slums, Shiite Muslim clerics have rushed to fill the power vacuum created by Saddam’s fall and the U.S. failure to provide postwar security. The latest example: Last week, the influential Iraqi Ayatollah Mohammed Baqir al-Hakim returned from exile in Iran to seek a role in Iraq’s political future.

Shiites make up 60 percent of Iraq’s population, and many are secular, but the best organized political movements are religious. Suddenly, the Bush administration, which predicted Iraq would become the first Arab democracy, faces popular clerics who reject Western liberal ideas.

How the administration handles this challenge may determine whether Iraq can meld Islam with some form of democracy – or becomes another venue for suicide bombs.

One of the trickiest questions is whether the Bush team should woo Shiite political groupings into the political process. Key secular Iraqi exiles such as Kanan Makiya, with close ties to Pentagon civilians, argue that Washington should help Iraq create a liberal-Western-style government that would separate religion and state. Clerics like Hakim have a very different concept.

Yet, if the United States excludes Shia political groups from the effort to shape an interim government, it runs the risk of alienating masses of religious Shiites. U.S. officials have had a tense relationship with Hakim’s Supreme Council for the Islamic Revolution in Iraq (SCIRI) because of its ties to Iran, but it remains one of seven Iraqi opposition exile groups charged with convening an interim national assembly. Another of the seven – newly added – is the Islamic Dawa party, whose spiritual leader was a famous ayatollah murdered by Saddam in 1980.

Are Hakim and the Dawa willing to play by democratic rules?

I interviewed Hakim in SCIRI’s Tehran headquarters in February. He told me: “I do want an Islamic state, but I do not impose this on people.” He said he accepted the principles agreed on at a U.S.-sponsored conference of exiles in London last December. These include the creation of a multiparty government that represents “all the Iraqi people, whether Shia, Sunni or Kurd,” along with democratic elections.

Hakim also said, in a rather amazing statement, that he would accept the people’s will, “even … a secular government.” Here comes the kicker, however. He added: “If you mean a secular government which is against Islam, we would not accept.”

What does this mean? It means that Hakim wants Iraq’s laws to be based at least partly on Islamic sharia law, which rules out many behaviors tolerated in the West. Haidar Abbas, a leader of the Dawa party, told me in a similar vein that he would oppose Western-style laws that prohibit discrimination against homosexuals or legalize prostitution.

Many secular Iraqi women are worried that Islamic parties will want women to veil, or seek divorce and inheritance laws based on Islamic precepts that discriminate against women. The key question is whether Islamic parties will push for constitutional provisions that compel religious adherence.

The good news is that Hakim and the Dawa say they don’t want an Iran-style regime, in which clerics have the final say on laws and a supreme cleric has the ultimate power. They also appear to reject the bloody tactics used by a third ambitious cleric, Muqtada al-Sadr, son of a another revered ayatollah whom Saddam murdered in 1999.

If key Shiite religious parties are inside the political tent, they may help marginalize rabble-rousers like the charismatic young Sadr, who has enthralled tens of thousands of young Shiites with his anti-American rants and calls for an Islamic state. Sadr is believed to have played a key role in the murder of a prominent pro-American cleric who advocated separation of mosque and state.

But there are no guaranteed outcomes. No Arab state has yet produced a constitutional democracy, let alone one that embraces Islamic characteristics. And all Shia political groups call for the speedy exit of American troops.

One sign the Bush administration now recognizes the nature of the problem: It has hired as an adviser a constitutional scholar named Noah Feldman, who has written a book called “After Jihad: America and the Struggle for Islamic Democracy. That struggle won’t be easy – for Iraqis or the United States.

Trudy Rubin is a columnist and editorial-board member for the Philadelphia Inquirer.