Now, however, Mr. Sharansky says that what is needed is for those returning Israelis to teach their compatriots what it means to be a Jew in the United States, where “pluralism,” the development of more liberal strains of Judaism beyond Orthodox, was a necessary strategy for surviving as Jews. Currently, secular Israelis, who face no threat of assimilation, see pluralism as a shortcut to the loss of Jewish identity.

“That’s where this misunderstanding begins,” he said.

And it can only end when enough Israelis understand the needs of the diaspora to support politicians who will do the same, he said. “Nobody’s against, but nobody’s really for” making compromises with the non-Orthodox Jewish streams, he said.

Mr. Sharansky has had quieter disagreements with Mr. Netanyahu. He obliquely scolds Israel’s government over its dalliances with hard-right nationalist governments in Eastern Europe, warning that just as “those who say they love Jews but hate Israel are not our friends, those who say they love Israel but hate Jews are not our friends either.”

He has also shown his own blind spots as a politician, and even as an evangelist for freedom — chiefly, his critics say, by seldom applying as critical a lens as he used against the Soviet Union to Israel itself. Writing in The American Conservative, Michael C. Desch accused Mr. Sharansky in 2005 of failing to show the “moral clarity” he demanded of others, instead demonstrating “moral ambiguity and inconsistency in his advocacy of democracy and human rights, particularly in the context of the Israeli-Palestinian conflict.”

Atop the indictment were Mr. Sharansky’s insistence that peace could be achieved only between Israel and a legitimately democratic Palestinian Authority — because real democracies do not try to kill one another, he argues — and his rejection of seemingly any peace initiative that required territorial concessions.

To be sure, Mr. Sharansky is quick to acknowledge the suffering of Palestinians, but he lays it at the feet of the entire international community, not Israel alone. “It is a thousand times more difficult to be a dissident among the Palestinians than among the Soviets,” he said.

“There, you knew that even if you will be isolated, you are part of a much bigger world of free thought, and this world is with you. Here, who cares?”