Some say they don't want to trigger a bitter civil war. Others say they want to follow the rebbe's teachings and not stand in judgment of another Jew.
Many Chabad leaders who worked with Schneerson acknowledge that they once believed he had the potential to be a Messiah, but that hope ended with his death.
The leaders said they did not name a new rebbe because no candidate appeared to match Schneerson's magnetism and depth. The movement is now headed by a council.
Critics see another possibility: A new rebbe would undermine the messianic attachment to Schneerson.
"This is the dominant aspiration," said Jacob Neusner, a professor and senior fellow at Bard College's Institute of Advanced Theology in New York.
Some critics say the movement's success has caused thousands of Jews who support Chabad or attend its programs to unwittingly donate money and energy to an effort that is akin to a dangerous cult.
The belief in a resurrected Messiah could distort Judaism "profoundly and perhaps permanently," said Berger, the Orthodox rabbi and history professor.
Supporters of Chabad dismiss such talk. "In our area, it's a nonexistent issue," said Jeffrey Lee Cohen, a 48-year-old real estate investor who has attended the Chabad Shul Potomac in Maryland for 16 years.
Rabbi Mark Miller, who runs a Reform synagogue in Newport Beach, has enrolled two of his children in a Chabad day school. He said guilt animates Chabad's critics. They "see Chabad and Orthodoxy in general as fidelity to ways of the past that many people had broken with. And that weighs upon them."
Those who support Chabad without joining the organization praise its success in touching people's lives.
George Rohr, a New York investment manager, gives an estimated $12 million a year to Chabad projects around the world.
"Where were we going to get the biggest bang for the buck?" Rohr asked. "The track record of Chabad in terms of bringing the light of Judaism and the warmth of Torah around the world is unparalleled."
In keeping with Schneerson's ideas, Jews exploring their faith in Chabad centers don't have to accept all -- or any -- of the group's Orthodox practices. They need not join a synagogue or pay dues.
"I was adamantly against going" to Chabad, said Melissa Breiter, a 39-year-old mother of three who attends Congregation Beth Meir HaCohen-Chabad Center of Yorba Linda.
Her parents were Reform Jews whom she describes as anti-Orthodox. But Chabad, she said, is "Judaism at its heart -- what it should be."
In Aspen, Colo., Rabbi Mendel Mintz, a Chabad emissary, said his center attracts 30 to 50 worshippers in peak seasons.
But Chabad recently bought an entire block on the town's Main Street for $6.3 million with contributions from Jews -- mostly neither Orthodox nor Lubavitchers -- who live full time or part time in Aspen.
The idea is to create a 16,000-square-foot center for the town's Jews to attend services, enroll their children in the preschool or take Mommy and Me classes.
"I feel very honored and blessed that I'm part of the rebbe's army to reach out to every Jew no matter their level of observance," said Mintz, who began Chabad in Aspen five years ago. "It's been really miraculous."
