UCHANAN, N.Y., April 23 It would have been a moment for the cameras, if only enough had shown up. As a flotilla of boats lined up here on the Hudson River in September 1997, the demonstrators aboard unfurled a bright yellow cloth emblazoned with "Crime Scene" in black marker in front of the Indian Point nuclear power plant.

But the world was mourning the death of Diana, princess of Wales, and almost no one other than the most committed of opponents gave much thought to the hulking nuclear plant on the Hudson. So the publicity effort organized by environmental and antinuclear groups went largely unnoticed.

How things have changed. Since the Sept. 11 terrorist attacks, growing anxiety over the safety of nuclear power plants has transformed Indian Point from a fringe issue that only antinuclear crusaders care about to a mainstream concern, and not just for Westchester suburbanites, but for New York City and New Jersey residents, who had, until now, barely registered the plant's existence 40 miles north of Midtown Manhattan.

This month alone, a headline in The New York Observer asked, "Chernobyl-on-Hudson?" In Bergen County, N.J., The Record published an article with the headline "Generating Fear: Indian Point Casts Nuclear Shadow Over North Jersey."

The news media scrutiny reflects probably the biggest groundswell of opposition to Indian Point since its two working reactors started generating nuclear power in the 1970's, and one that has a growing number of residents calling for the plant's closing. Some 20 million people live within 50 miles of the plant, putting it near more people than any other nuclear plant in the country.

The evacuation plan for the plant covers a 10-mile radius from the plant, but the federal government also has emergency readiness plans for a 50-mile "ingestion plume pathway" that includes New York City.

"On Sept. 11, my whole sense of safety and security went down with the World Trade Center," said Maureen Ritter, 44, who lives in Suffern, N.Y., exactly 12.3 miles on the other side of the Hudson from the plant. She knows because she recently calculated the distance on a map.

"Once you open your eyes, you can't shut them," Ms. Ritter said. "Believe me, I want to go back to finding matching socks for my children to wear in the morning, but I can't turn back."

So Ms. Ritter and many others have taken a stand against Indian Point. More than a dozen grass roots groups in Westchester, Rockland and New York City are opposing the plant.

A Web site for the New York City Campaign to Close Indian Point (nyccloseindianpoint.org) lists forums in churches in Greenwich Village, the South Bronx, and Park Slope in Brooklyn, and asks visitors to fill out an online petition.

These community groups have banded together with environmental and civic organizations as the Indian Point Safe Energy Coalition to work toward the goal of decommissioning the plant. Riverkeeper, an environmental group best known for protecting the Hudson, has led the fight by raising $100,000 in donations, including about $25,000 from Rockefeller family members and foundations.

It has also released a Marist Institute poll that showed that the majority of respondents who live within 50 miles of the plant want it shut down.

Alex Matthiessen, executive director of Riverkeeper, said that since Sept. 11, his staff had received dozens of calls and letters from people who were concerned about the vulnerability of Indian Point's nuclear operations. Riverkeeper decided to respond. In the past, the group had mainly criticized Indian Point for killing fish in the Hudson. "This has not been a movement driven by antinuclear groups," he said.

A growing number of local and state politicians have also joined the movement to close Indian Point, including Representative Nita M. Lowey and the two Democratic gubernatorial candidates, Andrew M. Cuomo and State Comptroller H. Carl McCall. Many others have voiced concerns about the plant. Gov. George E. Pataki, who grew up in Peekskill, just north of the plant, has not called for Indian Point to be closed, but has asked the federal government to reassess emergency guidelines for the plant.

Senator Hillary Rodham Clinton is sponsoring a bill that would tighten security at Indian Point and other plants, expand the evacuation area, and stockpile potassium iodide tablets to protect residents from radiation-induced thyroid cancer. She visited Indian Point for the first time after the Sept. 11 attacks.

"I think it certainly makes it very clear to me that building a plant in such a highly populated area raises serious issues," she said.

Indian Point's owner, the Entergy Corporation, has countered with a multimillion-dollar advertising campaign in newspapers and radio that is intended to reassure the public. It has dropped the word "nuclear" from its name. Entergy made that change on Sept. 6, after buying the reactors from separate owners and uniting the work forces. Now the message is: "Indian Point Energy Center. Safe. Secure. Vital."

Indian Point workers themselves have rallied against what they call the "campaign of misinformation" and "fear-mongering" by nuclear opponents. Mark Williams, a union coordinator for 600 workers at the plant, said they should know better than anyone if the plant is safe.

"It's very frustrating, because we work there," he said. "They tend to make us out as ignorant canaries going into the mines. In reality, we're a well-educated, highly trained, professional work force."

For years, antinuclear groups and others have railed against Indian Point's safety lapses, including a February 2000 radioactive leak that forced the Indian Point 2 reactor to shut down for nearly a year. As a result, the Nuclear Regulatory Commission heightened its scrutiny of Indian Point 2, and assigned it the worst performance rating of any reactor in the nation. (By contrast, the Indian Point 3 reactor is one of 73 plants that have the top performance rating.)

But it was only after Sept. 11, when one of the planes that hit the World Trade Center flew along the Hudson almost directly above the plant, that the potential dangers of Indian Point became real for most people.

The specter of a plane crashing into Indian Point sent shivers through sleepy enclaves up and down the Hudson, and gave anxious New York City residents and others something else to worry about. Even those who had never given much thought to Indian Point became openly fearful after diagrams of American nuclear plants were discovered in Qaeda strongholds in Afghanistan.

Allegra Dengler, a Dobbs Ferry trustee, said that once she started learning about Indian Point, she became concerned about not only terrorism, but also the effects of low-level radiation and other problems. Now her aim is closing Indian Point, even if that increases the price of electricity.

"People always care when their bills go up," she said. "But you have to weigh that against the risks."

Ellen Wang, 27, who lives on the Upper West Side, said she downloaded a flier from the New York City Campaign to Close Indian Point Web site that listed the top 10 reasons. No. 1 was "It's too close!"

She posted the flier on her bedroom door. "I don't worry about it all the time," she said. "But when I do, I get scared. It could be worse than Sept. 11."