In Iran, it seems, old antishah politicians never die. They just go underground.

Commensurate with the Moslem clergy's steady consolidation of power in the 16 months since the February 1979 revolution has been the disappearance of the secular moderates and liberals, the heirs of Mohammed Mossadegh's early 1950s National Front, who were originally at the forefront of the movement that toppled the shah.

It has become part of the Islamic republic's revolutionary mythology that the mullahs launched the movement. In fact, it was the very people that Ayatollah Ruhollah Khomeini and his clerical followers now scorn, Iranian intellectuals, who in the late summer and fall of 1977 began to test the limits of the shah's authority and organized the first major antigovernment demonstrations in public in 14 years.

While people like Abol Hassan BaniSadr, now president, and Sadegh Ghotbzadeh, now foreign minister, were in self-imposed exile in Paris, while Khomeini was in shah-imposed exile in Iraq, and while most to the mullahs who now hold high positions were in obscurity, the dissident politicians of the old school began to speak out in Iran against the shah at the risk of arrest, beatings, bombing or worse.

Their mistake, some now admit, as to rally behind Khomeini for the sake of unity, thinking that he and his clerical followers would retire to Qom after the shah was overthorwn and let them run the country.

During 1978, the old National Front politicians and other moderates lost the leadership of the antishah opposition movement to the militant Moslem clergy, which proved better able to channel public discontent and succesfully put forward Khomeini's ill defined concept of an Islamic republic as an alternative to the monarchy.

The National Front chiefs failed to mobilize the public as Mossadegh had, and young Iranians complained that the group was stodgy and unwilling to share authority with them.

Like many other Iranians who sought to replace the shah's dictatorship with a democracy, these moderate leaders underestimated the mullah's willingness to get involved in politics.

Where are they now?

Some of th moderates have gone into hiding in Iran after clerical calls for their arrest. Others have fled the country. Some have been jailed and several have joined the new regime in some capacity. Two prominent ayatollahs who are out of favor with the current rulers are under virtual house arrest in Qom.

The disappearance of the moderates has left Iran's middle class virtually leaderless. The result has been polarization and a leftward drift by many moderates who expected the revolution to bring democracy to Iran.

Lately the left too has fallen under the clerical steamroller, and some groups have been forced underground. A notable survivor has been the pro-Moscow Tudeh Communist Party, whose line has been to staunchly support Khomeini despite glaring ideological incompatibilities.

The eclipse of the Iranian moderates began a year ago when demonstrations against clerical abuses were broken up by club-wielding mobs of Khomeini supporters unleashed by right-wing clerics.

The seizure of the U.S. Embassy by militant Moslems Nov. 4 gave new impetus to the drive against the moderates, and several were denounced through the publication of embassy documents describing their contacts with American diplomats.

The embassy seizure also precipitated the resignation of the relatively moderate government of prime minister Mehdi Bazargan, a former member of the National Front.

In recent weeks the National Front has come under renewed pressure because of the election to the new parliament of five candidates associated with it. Three of them were later disqualified, and the other two are reportedly under pressure to resign. One, Rear Adm. Ahmad Madani, finished a distant second in January's presidential election.

The clergy's relentless campaign against secular Iranian moderates has been motivated by Khomeini's disdain for Westernized intellectuals, who represent to him a decandent Western cultural influence in Iran that is more dangerous to his notion of Islamic purism than communist politics.

"The present regime cannot tolerate intellectuals," a moderate dissident politician said. "Khomeini repeatedly insults them. In Persian the word for intellectual is rowshan feker, which literally means 'open-minded.' But Khomeini always adds garbzadeh, which means 'hit by the west.'"

It is perhaps for this reason that when Bani-Sadr and other lay political figures speak in public these days, they make a point of talking a working-class Persian.

Bani-Sadr, who worked on an unfinished doctorate for a dozen years in Paris, also abhors wearing a tie. Foreign Minister Ghotbzadeh, on the other hand, who was expelled from college in the United States but now dresses natily in three-piece suits, runs no risk of being considered -- or denounced as -- an intellectual.

The first of the old moderates to disappear was Shahpour Bakhtiar, a French-educated dissident who described himself as an "unemployed intellectual" before accepting the shah's offer to become prime minister in the last weeks before the revolution.

That decision, aimed at heading off what had become by then an irresistible rise to power of a staunch Islamic regime, cost Bakhtiar his standing in The National Front Political grouping, which repudiated him. After the revolution, Bakhtiar went into hiding, then managed to slip out of the country. He now resides in Paris.

His successor as head of the front's Iran Party, Abolfazl Qassemi, was elected to the new parliament in the first round of voting in March, but his victory was annulled on unsubstantiated charges that he was a member of the shah's secret police, SAVAK.

Qassemi denies the accusation and says the action against him shows that the authorities cannot tolerate "the slightest opposition in the parliament.

Another leading moderate laid low by the mullahs in hedayatollah Matin-Daftrai, leader of the National Democratic Front. He is a grandson of Mossadegh, who, while serving as prime minister, ousted the shah in 1953 in the name of nationalism and was in turn overthrown shortly after when the shah, with the help of the American CIA, returned to the throne.

The National Democratic Front emerged as more dynamic than the crusty National Front after the revolution and began to attract a large following among the middle class. It was dismantled by Khomeini supporters after it organized large street demonstrations in August.

A warrant was issued for Matin-Daftari's arrest, and he went underground. Some reports say the left the country.

Rahmatollah Moghaddam-Marghei, anotehr early antishah activist, was named governor general of his native Azerbaijan province after the revolution but resigned in protest as the contry drifted toward clerical rule. When an assistant revolutionary prosecutor came to arrest him late last year after he was denounced by the militants occupying the U.S. Embassy, he reportedly locked the man in his house and disappeared.

Hassan Nazih, the former head of the Iranian Bar Associatin and the first oil minister after the revolution, also became a victim of the mullahs' housecleaning after he began to speak out against the danger of "clerical dictatorship."

He left his post and went underground last September when influential clerics in Khomeini's entourage called for his arrest, and he recently surfaced in Paris. Nazih, 59, told a news conference there that during his 25 years of oposition to the shah in Iran he did not recall having met many of the Islamic revolutionaries who now hold power.

Among the moderates jailed in the year after the revolution were leaders of the Moslem People's Republican Party sponsored by Ayatollah Kazem Shariatmadri.

The party was condemned by its more powerful pro-Khomeini rival, the clergy-led Islamic Republican Party, after supporters demonstrated in Qom and Tabriz. The fate of the party's secretary general is in some dispute, wth authroities saying he has been arrested and supporters asserting he is in hiding.

Shariatmadari has been queiscent since his criticisms of the regime ignited the troubles. At least two of his aides have been reported killed by opponents, and he is said not be free to leave Qom.

The leader of Iran's Shiite Arabs, Ayatollah Taher Shobeir Khaqani, also is said to be under house arrest in Qom. His supporters have charged that he was abducted by Revolutionary Gards from his home in Khorramshahr in his native Khuzestan Province after Iranian Arabs seeking regional autonomy rebelled there a year ago.

Bakhtiar, Qassemi, Matin-Daftari, Moghaddam-Maraghei and Nazih were all members or supporters of both the National Front and the Iranian Human Rights Association, the main dissident groups active in Iran in late 1977.

The National Front organized a demonstration by bazaar merchants that fall in which, ironically, they called publicly for Khomeini's return from exile for the first time since the shah expelled him for opposition activities in 1964.

Shortly after that, a National Front meeting on the outskirts of Tehran was brutally broken up by SAVAK. At about this time too, students gathering to hear lectures by dissident intellectuals such as poets and writers were attacked by government agents, and campus demonstrations and strikes started to protest the closing of libraries at Tehran University.

Not until January 1978 did the Moslem clergy in Iran fully throw in its lot with the new dissident movement when police fired on religious demonstrators in Qom. Ironically, it was the moderate Shariatmadari who led the chorus of clerical protests. Only afterward did the pronouncements of Khomeini, who had consistently opposed the shah from exile, begin to have an effect as cassette tapes of his speeches were widely distributed.

Among the early activists who joined forces with the Khomeini regime have been Mehdi Bazargan and Dariush Foruhar, a National Front politician who briefly held the post of labor minister. Both have been relegated to behind-the-scenes roles since the Bazargan government fell.

Other National Front figures such as Karim Sanjabi and Gholam Hossein Sadighi have slipped into obscurity after breaking with the revolutionary government early on.

Besides neutering Iran's middle class, the disappearance of the moderates has also left the government and various clergy-minded revolutionary in stitutions largely in the hands of exiles and Johnny-come-latelies who rose to prominence after the revolution.

"I'm so ashamed," one Iranian liberal who supported the revolution said recently. "Where did all these people come from?"