SOFIA, Bulgaria (AP) _ Reformists said Saturday no meaningful change can come to Bulgaria unless the new leadership relinquishes the Communist Party's ''divine right'' to power.

Todor Zhivkov, 78, stepped down Friday after 35 years as party chief and was replaced by Petar Mladenov, who served as foreign minister for nearly two decades and is considered more open to change. Mladenov is 53.

''If the Communist Party is shortsighted enough not to drop Article 1, Paragraph 2 of the constitution, then no radical change will be possible,'' said Petar Beron, a zoology professor and a leader of the ecological group Eco-Glasnost.

The paragraph gives the party the ''leading role'' in Bulgaria.

''They must give up their 'divine right' that 'we are here forever,''' Beron told reporters in his small office at the National Museum of Natural History.

Rumen Vodenicharov, who leads the Independent Committee for the Protection of Human Rights, championed freedom of speech, less censorship and disbanding of the all-pervasive secret police.

''Zhivkov must be publicly accused and punished for his serious mistakes,'' Vodenicharov, a research chemist, told The Associated Press.

He said Zhivkov's harsh treatment of the 1.5 million ethnic Turks in Bulgaria was his most serious mistake.

''Mladenov's handling of the Turkish issue, which is now our biggest problem, will be a litmus test of whether he is a reformer,'' he said.

Vodenicharov disclosed that several independent groups were sending a telegram to Mladenov expressing support for the change in leadership and announcing a rally in downtown Sofia on Monday afternoon.

''In principle, we welcome the changeover as the beginning of radical changes,'' he said. ''At the same time, we would like to warn the new leader that our position remains firm and close to all international (human rights) agreements the Bulgarian government has signed.''

He and Kostadin Georgiev, a philosopher, said the question remained whether the new party leader could break with his political past. ''After all,'' Georgiev said, ''Mladenov is the product of this system.''

Beron said: ''Mladenov is perhaps the best choice of the present set of people. He is much better educated than Zhivkov and has international experience.''

Mladenov ''could try to save the whole (party) machinery from crumbling by removing some of the most unpopular people,'' he said.

A new plenary session of the Central Committee is expected soon and probably will approve other changes in the top party ranks to strengthen Mladenov's position, the activists said.

''Bulgaria is not yet ready for pluralism, but should now be prepared for it,'' Beron said. He added that there were many thoughtful people in the country who could develop political programs.

Two new independent organizations have been formed this month, activists reported, adding to more than a dozen already campaigning for human rights and democratic reform.

The Priests' Union of Orthodox clerics, banned in 1957, was reorganized Wednesday, and former political prisoners in Plovdiv, Bulgaria's second- largest city, established the Club of People Sentenced Under Socialism, they said.

Activists claim 200 political prisoners are held in Bulgaria, a nation of 9 million people.