After a month of tumultuous rallies and motorcades that followed her return from exile, opposition leader Benazir Bhutto's campaign to topple the government has slowed somewhat.

Like the rest of life in Moslem Pakistan, politics is subdued during Ramadan, the Islamic month of fasting. Although Bhutto's camp says it will force a direct confrontation with the authorities after Ramadan ends in early June, Prime Minister Mohammed Khan Junejo is confident that Bhutto's campaign is already fizzling.

Many Pakistanis and foreign observers fear the results of a confrontation between the government and Bhutto, 33, whose father, Zulfiqar Ali Bhutto, was overthrown as prime minister in 1977 by Mohammed Zia ul-Haq, who is now president, then arrested and executed. They fear it would threaten Pakistan's cautious traverse from military rule to civilian parliamentary democracy, by deepening the country's political polarization and leading to civil violence that could prompt the Army to take back power.

Bhutto returned from exile last month, calling for Zia to resign and permit new elections this fall on a party basis. Since Zia ended 8 1/2 years of martial law in December, allowing civilian politics to resume, Bhutto and Junejo have emerged as the two leading political combatants.

The People's Party, which Bhutto had led from exile, embraces Pakistanis of varying political views, including confirmed radicals and wealthy, traditional landholding families such as the Bhuttos. But she has been trying to gain control of its apparatus by naming her own generally more leftist loyalists in place of older, more established party leaders.

The contest between Junejo, a calm and soft-spoken political conservative, and Bhutto, a fiery orator who speaks of a revolution in Pakistani politics, is billed by one Pakistani political analyst here as "the manager vs. the Messiah."

Last year, Junejo won a National Assembly seat in nonpartisan elections called by Zia. After the elections, which Bhutto and her opposition allies boycotted, Zia named Junejo prime minister.

At the time, many Pakistanis and foreign observers questioned how firmly the quiet Junejo would establish his authority under Zia, who retained broad powers and direct control of the Army when he returned constitutional rule.

Now, both diplomats here and Pakistani analysts say Junejo appears to be in control of most government policy and, after 14 months in office, is making progress in building a national political base.

Junejo has also been praised widely for establishing what many Pakistanis call the freest political atmosphere since Pakistan first fell under military rule in 1958.

In an interview last week, Junejo said he and the Reagan administration are "finalizing the dates" for an official visit to Washington, probably in July. Following a stream of senior U.S. military officers and Reagan administration officials here during the past year, a Junejo visit would underline Washington's interest in Pakistan as a strategic ally, and its desire to build ties with the new civilian administration.

A Junejo trip to the United States would also accord with what Pakistani analysts say is Zia's continued domination of foreign policy. The Reagan administration would likely use such a visit to repeat its support for the transition to Junejo's civilian government, although many observers here, noting a strong public current of anti-U.S. sentiment, suggest that a close identification with Washington might hurt Junejo in his domestic struggle with Bhutto.

Zia claims a mandate to rule as president until 1990. Bhutto challenges both Zia's and Junejo's legitimacy, saying last year's elections were unfair because they excluded organized parties.

Junejo conceded last week that Bhutto has drawn big crowds, but he argued that they have been stage-managed to exaggerate her popular support. He said Bhutto's Pakistan People's Party had spent "huge amounts" to transport supporters long distances to her rallies.

Bhutto has avoided attacking Junejo, focusing instead on the legitimacy issue and trying to attract support as the symbol of opposition to the widely unpopular Zia. But Junejo said Bhutto has failed to build a groundswell of support because her party and smaller allied opposition parties of the Movement for the Restoration of Democracy "did not have any program."

"They couldn't say that 'the government of Mr. Junejo, during the last one year, could not solve all these major issues, or any one, and they are not fit to hold this position,' " Junejo said.

As he has before, Junejo made it clear that he wants to avoid a direct confrontation with Bhutto.

During the past month, police and other authorities who are under his direction have kept a low profile at her rallies, and Junejo suggested that problems arising from her traffic-choking processions should be resolved by the People's Party itself.

At the same time, Junejo rejected a possible avenue for compromise, denying suggestions that he might call the elections demanded by Bhutto if his party, the newly revived Pakistan Moslem League, fails to win a majority of the seats in next year's local elections.

But Junejo, who has been guiding the authorities' response to Bhutto's campaign, will come under heavier pressure next month when the People's Party plans what Bhutto calls a calculated move to force the government to concede her demands or take repressive measures against her supporters.

Until Ramadan ends, Bhutto will focus on organizational and strategy meetings with her senior aides at her home in Karachi.

However, Bhutto spokesman Salmaan Taseer said last week, "After Ramadan, [the government] will have to bow to our pressure. We might hold sit-ins or perhaps . . . march from Lahore to Islamabad and surround the National Assembly building."

"Especially if we do it in five or six cities at the same time, they will have to concede," said Taseer, in a telephone interview from Lahore. He stressed that precise tactics and schedules for confronting the government remain unsettled.

For most analysts here, the probability of a serious political confrontation remains unclear. Pakistani journalists and other observers said Bhutto's crowds have included many curious onlookers who would not likely answer a call for civil disobedience or strikes, and both the official response and public reaction to such a campaign are uncertain.

Junejo has said repeatedly that the authorities will not interfere with Bhutto's campaign as long as she obeys the law. In the interview, he played down the possibility of a serious confrontation.

In their contest, "Bhutto and Junejo are offering Pakistanis two completely different kinds of leadership," according to Ijaz Gilani, of the Pakistani Institute of Public Opinion. Gilani said that Pakistani voters, 70 percent of whom live in villages, traditionally have chosen their local officials as advocates or intermediaries with the government, to improve utility services or schools and to unsnarl problems with plodding bureaucracy.

In reestablishing the Moslem League, the nationalist party founded by Mohammed Ali Jinnah, Junejo began by organizing the overwhelmingly conservative members of the National Assembly into a parliamentary party. Now, in a membership drive, he is trying to reach voters through a network of traditional local leaders -- landlords or religious or tribal notables.

"Junejo has been pushing the local leaders very hard to work with him on improving social services at the local level, and to distribute government-owned land to urban squatters," said a western diplomat.

Another diplomat, pronouncing himself impressed with Junejo's party building, warned that "it is still in the early stages. Junejo's task now is to make his machine politics work, to reduce corruption and get the bureaucracy to deliver on his promises."

Pollster Gilani said Bhutto is working in the opposite direction from Junejo, with a "messianic appeal" directly to voters, whose support she is then using to attract local politicians.

"She and Junejo are building two completely different kinds of political power," he said.

The two leaders' differences in style are no less striking. Unable to deliver her message over state-controlled radio or television, Bhutto has organized massive rallies and is happy to arrive hours late after a slow motorcade through crowds of supporters.

In her appearances, she often displays jubilation or anger, and her emotional speeches skirt specific policy questions, calling instead for a peaceful revolution to implement what she calls "the people's will."

Junejo is a bland speaker who shows little emotion and focuses on organizational politics. From a landholding family of Sind province, as is Bhutto, he is a religious disciple of a conservative Moslem holy man.

Junejo studied agriculture in Britain and returned 30 years ago to begin his political career in his home village. Even his opponents do not question his integrity, which is thought to be a major reason why Zia chose him to manage the transition to civilian rule.

In the interview at his official retreat in the mountain resort of Murree, 31 miles north of here, Junejo spoke so quietly that a tape recorder in front of him barely picked up his voice. Sometimes reflecting briefly before answering questions, Junejo noted that Pakistan has had three periods of martial law and blamed the failures of civilian rule on individual leaders, including Zulfiqar Ali Bhutto, who, he said, had tried to gather too much authority and had stifled the country's parliamentary system.

Junejo says now that civilian rule has returned despite their boycott of the process, Bhutto and her allies want elections, not to advance democracy, but simply to take power. "The parties that are shouting now that there should be elections, who stopped them not to [contest in the elections last] year?" he asked. "It is their own fault," he said. "They should only wait for a time and when the next election takes place, they're welcome."