Her parents, she said in a telephone interview, are "courageous" and "trying very hard," but have been slow to explore alternative approaches.

"You can say it and say it and say it," she said. "Show me evidence that they're actively researching vaccines."

The Wright family's fight has captured the attention of the bloggers, who are now questioning everything from its office lease to how it makes grants. The charity rebutted the bloggers' accusations of improprieties in interviews with The New York Times, which examined its IRS forms and read relevant sections to Gerald A. Rosenberg, former head of the New York State attorney general's charities bureau. He said nothing he reviewed was untoward.

The most distinctive aspect of Autism Speaks is its gobbling up of Autism Coalition for Research and Education, an advocacy group; the National Alliance for Autism Research, devoted to scientific research into potential genetic causes, with high standards for peer review; and Cure Autism Now, which has championed unconventional theories and therapies.

Which wing of the merged charity is ascendant? Some establishment scientists and parents now fear it is the Mercurys.

They point to Cure Autism Now's having more seats than the National Alliance does on the board of directors and the growing number of research projects that focus on environmental causes.

At a recent benefit gala, featuring Bill Cosby and Toni Braxton, some in the audience were surprised when Bob Wright announced that all proceeds would go toward environmental research, which generally includes vaccines.

But a list of current research grants on the Autism Speaks Web site suggests that the Wrights, while walking a fine line, are leaning toward genetic theories.

Between 2005 and 2007, the charity sponsored $11.5 million in grants for genetic research (compared with $5.9 million by all its partners between 1997 and 2004). It sponsored $4.4 million in environmental research (down from $6 million granted by the partners in the prior seven years). And many of the environmental studies explore what is known as the double-hit hypothesis: That the genes for autism may be activated in some children by exposure to mercury or other neurotoxins.

Bob and Suzanne Wright say their two-year immersion into the world of autism has been an eye-opener, especially the heated arguments worthy of the Hatfields and McCoys.

Suzanne Wright is aware that the marriage of the alliance and Cure Autism Now, for instance, could fall apart over opposing ideologies.

"I'm not going to let it," she said. "The truth will rise to the top."

She is also aware that the rift in her own family needs repair: on June 15, her daughter posted a message on an autism Web site questioning their "personal denouncement of me."

Yet Suzanne Wright is confident that "we'll work our way through this." Autism, she said "has done enough damage to my family. I'm not letting it do any more."