In the emerging post-Qaddafi Libya, the most influential politician may well be Ali Sallabi, who has no formal title but commands broad respect as an Islamic scholar and populist orator who was instrumental in leading the mass uprising.

The most powerful military leader is now Abdel Hakim Belhaj, the former leader of a hard-line group once believed to be aligned with Al Qaeda.

The growing influence of Islamists in Libya raises hard questions about the ultimate character of the government and society that will rise in place of Col. Muammar el-Qaddafi’s autocracy. The United States and Libya’s new leaders say the Islamists, a well-organized group in a mostly moderate country, are sending signals that they are dedicated to democratic pluralism. They say there is no reason to doubt the Islamists’ sincerity.

But as in Egypt and Tunisia, the latest upheaval of the Arab Spring deposed a dictator who had suppressed hard-core Islamists, and there are some worrisome signs about what kind of government will follow. It is far from clear where Libya will end up on a spectrum of possibilities that range from the Turkish model of democratic pluralism to the muddle of Egypt to, in the worst case, the theocracy of Shiite Iran or Sunni models like the Taliban or even Al Qaeda.

Islamist militias in Libya receive weapons and financing directly from foreign benefactors like Qatar; a Muslim Brotherhood figure, Abel al-Rajazk Abu Hajar, leads the Tripoli Municipal Governing Council, where Islamists are reportedly in the majority; in eastern Libya, there has been no resolution of the assassination in July of the leader of the rebel military, Gen. Abdul Fattah Younes, suspected by some to be the work of Islamists.

Mr. Belhaj has become so much an insider lately that he is seeking to unseat Mahmoud Jibril, the American-trained economist who is the nominal prime minister of the interim government, after Mr. Jibril obliquely criticized the Islamists.

For an uprising that presented a liberal, Westernized face to the world, the growing sway of Islamists — activists with fundamentalist Islamic views, who want a society governed by Islamic principles — is being followed closely by the United States and its NATO allies.

“I think it’s something that everybody is watching,” said Jeffrey D. Feltman, assistant secretary of state for Near Eastern affairs, visiting here on Wednesday. “First of all the Libyan people themselves are talking about this.” The highest-ranking American official to visit Libya since Colonel Qaddafi’s fall, Mr. Feltman was optimistic that Libya would take a moderate path.

“Based on our discussions with Libyans so far,” he said, “we aren’t concerned that one group is going to be able to dominate the aftermath of what has been a shared struggle by the Libyan people.”

Mr. Sallabi, in an interview, made it clear that he and his followers wanted to build a political party based on Islamic principles that would come to power through democratic elections. But if the party failed to attract widespread support, he said, so be it.

“It is the people’s revolution, and all the people are Muslims, Islamists,” Mr. Sallabi said. Secularists “are our brothers and they are Libyans.”

“They have the right to offer their proposals and programs,” he said, “and if the Libyan people choose them I have no problem. We believe in democracy and the peaceful exchange of power.”

Many Libyans say they are not worried. “The Islamists are organized so they seem more influential than their real weight,” said Usama Endar, a management consultant who was among the wealthy Tripolitans who helped finance the revolution. “They don’t have wide support, and when the dust settles, only those with large-scale appeal, without the tunnel vision of the Islamists, will win.”

Yet an anti-Islamist, anti-Sallabi rally in Martyrs’ Square on Wednesday drew only a few dozen demonstrators.

Many, like Aref Nayed, coordinator of the Transitional National Council’s stabilization team and a prominent religious scholar, say that the revolution had proved that Libyans would not accept anything but a democratic society, and that the Islamists would have to adapt to that.

“There will be attempts by people to take over, but none of them will succeed because the young people will go out on the streets and bring them down,” Mr. Nayed said.

Some are concerned that the Islamists are already wielding too much power, particularly in relation to their support in Libyan society, where most people, while devout, practice a moderate form of Islam in which individual liberties are respected.

Mr. Sallabi dismissed those fears, saying Islamists would not impose their traditionalist views on others. “If people choose a woman to lead, as president, we have no problem with that. Women can dress the way they like; they are free.”

Adel al-Hadi al-Mishrogi, a prominent businessman who began raising money for the anti-Qaddafi insurgents early in the revolution, is not convinced by the Islamists’ declarations of fealty to democratic principles. He pointed to a well-organized Islamist umbrella group, Etilaf, which he said had pushed aside more secular groupings.

“Most Libyans are not strongly Islamic, but the Islamists are strongly organized, and that’s the problem,” Mr. Mishrogi said. “Our meetings go on for hours without decisions. Their meetings are disciplined and right to the point. They’re not very popular, but they’re organized.”

He complains that Etilaf and Mr. Sallabi are the ones who are really running things in Libya now. Others say the picture is much more diverse and chaotic than Mr. Mishrogi suggests, although it is true that Etilaf, with no fixed address and still apparently operating underground, continues to issue decrees of all sorts as if it were some sort of revolutionary guide.

“All offices here must make sure that they are headed by an acceptable person within seven days of this notice,” read a leaflet pasted to the doors of offices throughout Tripoli Central Hospital, dated Sept. 3 and signed, simply, Etilaf.

“They are behind everything,” Mr. Mishrogi said.

Youssef M. Sherif, a prominent Libyan writer and intellectual, said: “Every day the Islamists grow stronger. When there is a parliament, the Islamists will get the majority.”

“Abdel Hakim Belhaj is in effect the governor of Tripoli just because he was elected by an Islamist militia,” Mr. Sherif said. Echoing debates in Egypt, Mr. Sherif argued for a longer transition to elections than the planned eight months, to give liberals a better chance to organize.

The growing influence of the Islamists is reflected in their increased willingness to play a political role. Until recently the Islamists have kept a low profile, and even many secular Libyan officials have expressed a reluctance to criticize them, saying they should focus instead on the common enemy while Colonel Qaddafi remains on the loose.

That seems to be changing. After the interim government’s acting prime minister, Mr. Jibril, appeared recently in Tripoli and indirectly criticized politicking by the Islamists as premature with a war still in progress, Mr. Belhaj and Mr. Sallabi began agitating for his replacement.

“Jibril will be gone soon,” one aide to Mr. Belhaj said.

And Mr. Sallabi said that Mr. Jibril, along with the American-educated finance and oil minister, Ali Tarhouni, were ushering in a “new era of tyranny and dictatorship,” Al Jazeera reported.

During the 42 years of Colonel Qaddafi’s rule, underground organizations like Mr. Belhaj’s Libyan Islamic Fighting Group and the Muslim Brotherhood were the only opposition. Although outlawed and persecuted, they had a network through mosques that secular opponents of the government could not match.

That has also given them a head start in political organizing now, and they appear to be wasting no time.

“There will be attempts by some parties to take over; it’s only natural,” said one prominent official with the Transitional National Council, who spoke anonymously so as not to alienate Islamists. “And definitely Etilaf is trying to increase its influence. And we’re hearing much more from the Islamists in the media because they are more organized and they are more articulate.”

Mr. Nayed conceded that might be true, but was unconcerned. “My answer to anyone who complains about that: You must be as articulate as they are and as organized as they are,” he said. “And I think we’re starting to see that among various youth groups.”

Fathi Ben Issa, a former Etilaf member who became an early representative on the Tripoli council, said he quit his position after learning that the Muslim Brotherhood members who dominate that body wanted to ban theater, cinema and arts like sculpture of the human form. “They were like the Taliban,” he said. “We didn’t get rid of Qaddafi to replace him with such people.” The final straw, he said, came when Etilaf began circulating a proposed fatwa, or decree, to bar women from driving.

Most Libyans are quick to bristle at suggestions that their own Islamists might one day go the way of Iran, where after the fall of Shah Mohammed Reza Pahlavi, Ayatollah Ruhollah Khomeini stomped out a short-lived liberal government by denouncing democracy as un-Islamic.

Mr. Sallabi said he hoped Libyans could find a leader on the model of George Washington, whom he had been reading about lately. “After his struggle he went back to his farm even though the American people wanted him to be president,” Mr. Sallabi said. “He is a great man.”

Referring to Mr. Sallabi, Mr. Ben Issa, who said he has received death threats since breaking with the Islamists, retorted: “He is just hiding his intentions. He says one thing to the BBC and another to Al Jazeera. If you believe him, then you don’t know the Muslim Brothers.”