Soviet troops are only prop for unpopular Afghan leader.

Afghanistan's new strong man, Babrak Karmal, has little to worry about as long as Soviet troops are here to protect his rule. But few see this communist politician as a leader loved and respected by his people.

"Karmal is known in Afghanistan as an atheist and not a patriot," says one of the exile guerrilla leaders in neighboring Pakistan. He vows that "Karmal will meet the same fate as Shah Shuja, who was installed by Great Britain in the 19th century."

Western diplomats in Kabul unanimously agree that Mr. Karmal is less popular and has less credibility than any of his predecessors.

After the pro-communist coup in April 1978 the People's Democratic Party of Afghanistan -- the country's pro-Soviet communist movement -- claimed to have 50 ,000 members. Independent estimates, however, range from 5,000 to 10,000.

"Karmal's No. 1 political problem is getting support from the people by whatever means," one senior Western ambassador said."Either he gets rid of the Russians, or he persuades the Afghanis that the Russians are not so bad after all." Other Western diplomats take a much more definite view of Mr. Karmal's future. "Whatever he does, Karmal will never be able to erase from people's minds that he was put in by the Soviet Army," a spokesman of this school of thought said.

Most diplomats estimate that Mr. Karmal has the support of no more than 5 percent of the population. "The people question his legitimacy and view him as an atheist who has sold himself completely to the Soviet Union," one analyst said.

Afghanistan's new leader, however, does appear to be aware of his lack of credibility. His supporters have launced a countrywide campaign to present him as the continuation and logical successor of Nur Muhammad Taraki, who was overthrown last September by his Deputy Prime Minister, Hafizullah Amin.

But several hundred people attending a rally Dec. 10 in Charikar, a small town 50 miles north of Kabul, hardly gave the impression of buying this approach.

Standing on a red-draped podium and flanked by a framed picture of Taraki, speaker after speaker supported Mr. Karmal's takeover from Mr. Amin, who was denounced as a "tool of the CIA" and as a "puppet of US imperialism." The crowd, guarded by heavily armed Afghan soldiers, did not clap more than perfunctorily.

"Muhammad Daoud was still a tribal leader," explained one Western diplomat, "Taraki was still local, but Karmal is simply foreign."

Precise knowledge about the guerrillas' activities is hard to obtain. Most observers point out that a lot of the information about the resistance stems from often-exaggerated claims by the guerrillas in Pakistan, which are then passed on as factual, confirmed information to Western embassies in the Afghan capital. Moreover, Kabul is a city bursting with rumors that often cannot be substantiated.

A probably classic example is last week's closure of the strategic Salang Pass for several days. Afghan Army officers in the village of Jabalserej, 80 miles north of Kabul, claimed that 400 to 500 Soviet soldiers had been killed in a rebel attempt to disrupt this important supply line for the Red Army.

An investigation of the facts, however, revealed that the pass had been closed after Soviet soldiers had entered Jabalserej at the foot of the Hindu Kush mountains and that only one soldier, an Afghan, was killed. This incident provoked anti-Soviet disturbances, which could hardly be described as organized guerrilla activities.

One incident, as was told to the Monitor by a usually reliable source, points out the guerrillas' dilemma. On Jan. 8, rebels ambushed the local bus from Jalalabad to Kabul and killed a number of Afghan travelers. The civilian passengers pleaded not to be shot, shouting, "we are Muslim. We are your brothers." The guerrillas, however, discounted this because, "You are going to Kabul instead of joining us with a gun in your hand."

Political analysts believe that the bitter struggle within Afghanistan's communist movement and the tenuous loyalties within the country's Revolutionary Council constiture the most serious danger to Mr. Karmal's rule. Western diplomats revealed recently that about 12 "senior officials of Mr. Karmal's Parcham Party or their immediate relatives" had been murdered since the Soviet-backed coup on Dec. 27.

These diplomats, however, refused to confirm or deny that immediate relatives of Mr. Karmal had been among the vicitims of this assassination campaign. They point to the fact that in early December 12 prominent officials of the Khalq party, which had been led by Hafizullah Amin, were killed in a similar campaign.

Western diplomats in Kabul and Afghan exile circles in New Delhi do not exclude the possibility of an internal coup against Mr. Karmal by members of his Revolutionary Council. "By the very nature of this government I am very skeptical about a consensus in the ruling elite," one diplomat said. He added that "probably he [Karmal] will have to be a dictator to be able to survive."