The Moslem revolutionaries running Iran are using the current anti-U.S. campaign to ask Iranians to unite and vote for the controversial constitution conferring virtually autocratic powers on Ayatollah Ruhollah Khomeini.

But despite the unity call -- and massive televised explanations by turbaned clerics -- opposition from various shades of political, religious and social belief has dared speak out, denounce the draft constitution and call for a boycott.

The outcome of the two-day vote on Sunday and Monday is not itself in question, but the margin of victory -- and especially the abstention rate -- is seen as the real yardstick of Khomeini's support.

"Khomeini and his friends have a lot of success with the masses," a leading opposition lawyer said recently."The silent majority agrees with them -- but not with the constitution they've concocted."

The calls for a boycott span the social and political spectrum from women opposed to what they fear will become their status as second-class citizens in Khomeini's Islamic republic, to westernized Iranians opposed to clerical rule and Kurds now virtually running their western province while negotiating formal autonomy with the central government.

But the most formidable opposition is that of Ayatollah Kazem Shariatmadari, a leading political moderate and de facto leader of the northwestern province of Azerbaijan where almost a third of Iran's population lives.

The importance of his Moslem People's Islamic Republic Party -- even outside his native province -- far outweighs boycott calls from other political parties. Those parties include the rightwing Pan-Iran Party, the middle-of-the-road National Front, the left-of-center National Democrats and armed guerrilla groups such as the radical Islamic Mujaheddin and the Marxist-Leninist Fedaye Khalq.

Shariatmadari's weekly newspaper Moslem People justified its boycott threat by saying that "all powers are put at the disposal of one person who is not responsible to anyone, while all responsibility is entrusted to those who lack power compatible with their responsibilities."

The draft's most controversial aspect is its implicit or explicit veto accorded what is called the Nations's guide. For the first time in Shiite Islamic history, The velayat-e-laghih, or religious guardianship of Islamic laws, is enshrined in constitutional form, Hitherto, Shiite Islam's messianic tradition has insisted that constitutional or temporal power could only be exercised by a religious leader when the 12th -- or hidden -- iman returned to ensure the reign of justice on earth.

Its principle 110 entrusts the leader with:

Selection of six religious lawyers for the 12-man Guardian Council, a kind of second chamber which rules on the constitutionally and Islamic correctness of all laws passed by the National Assembly. The other six members are mullahs.

Appointment of the highest judicial authority, supreme commander of the armed forces, appointment and dismissal of the chief of the joint staffs, chief commander of the Revolutionary Guard corps, senior commanders of all military services and the high council of national defense.

Declaration of war, peace and the mobilization of the armed forces.

Checking the qualifications and competence of presidential candidates, a duty shared with the Guardian Council.

Under the leader, a complicated structure is planned involving a president, prime minister, government with ministers, National Assembly and Guardian Council.

Surveying the draft, a prominent constitutional lawyer said, "I think they will be obliged to change the constitution simply because it cannot be applied. Look at the leadership pyramid -- there is not attribution of powers among them."

Since Khomeini's return from exile in February, liberal democrats have fought a losing battle with Khomeini and his clerics to maintain much of Iran's Western-style constitutional guarantees.

The original Western democratic-style draft was rejected by Khomeini in the spring and the much-touted broad constituent assembly never took place.

Then prime minister Mehdi Bazargan presented a compromise draft incorporating the original's main points and Khomeini's objections. But a less inclusive constituent assembly, called the Assembly of Experts, in turn rejected Bazargan's draft. The predominately clerical makeup of the assembly meant the clergy rode more or less roughshod over the handful of liberals still fighting a rear-guard defence of Western ideals.

But within days of the onset of the U.S.-Iranian crisis, the clerical majority rushed the assembly to complete its task, and took the finished draft constitution to the holy city of Qom, where Khomeini declared its 175 articles "a completely Islamic constitution."

Significantly, the referendum was scheduled on the heels of Tasua and Ashura, Shiite Islam's two holiest days during the Moharram month of mourning.

In one of his last acts as prime minister. Bazargan is reported to have told Khomeini that the constitution would not outlive the avatollah.