In a country with virtually no previous grass-roots political participation, where more than a hundred new or little-known political parties have raced to introduce themselves to the public, “it is a very fast track, and whatever means they have at their disposal is going to make a big difference,” said Eric Goldstein, a researcher with Human Rights Watch who has tracked Tunisia’s steps since the revolt.

Ennahda, which had a long history of opposition here before Mr. Ben Ali eviscerated it a decade ago, is widely expected to fare the best, and no one pretends that it owes its popularity only to its financial clout. Its moderate and modern brand of Islamic politics has struck a chord with many Tunisians.

But for months, it has been at the center of attacks from liberal rivals and liberal-leaning election officials who accuse it of taking foreign money, mainly from the Persian Gulf. Islamist groups from Egypt to Lebanon are widely believed to rely on such support from the wealthier and more conservative gulf nations, but the charges have resonated especially loudly in Tunisia, in part because regulators have sought to stamp it out.

“Everybody says that Ennahda is backed by money from the Arabian gulf,” said Ahmed Ibrahim, the founder of the liberal Democratic Modernist Pole coalition, calling the outsize influence of foreign money a threat to Tunisia’s “fragile democracy.”

Though Ennahda’s sources of financing have not been disclosed, its resources are evident. The first party to open offices in towns across the country, Ennahda soon blanketed Tunisia with fliers, T-shirts, signs and bumper stickers. Unlike other parties here, it operates out of a gleaming high-rise in downtown Tunis, gives away professionally published paperbacks in several languages to lay out its platform, distributes wireless headsets for simultaneous translation at its news conferences and hands out bottled water to the crowds at rallies.