Marie Bedford first saw what has become known as “The Ad” in nonprofit circles about a year and a half ago. “I saw it a couple of times and found I just had to respond,” Ms. Bedford, an actress living in Brooklyn, said. “It’s so moving.”

The television advertisement, for the American Society for the Prevention of Cruelty to Animals, features heartbreaking photographs of dogs and cats scrolling across the screen while Sarah McLachlan, the Canadian singer-songwriter, croons the haunting song “Angel” in the background.

That simple pitch has raised roughly $30 million for the organization since the advertisements started running in early 2007, making it the A.S.P.C.A.’s most successful fund-raising effort  and a landmark in nonprofit fund-raising, where such amounts are virtually unimaginable for a single commercial. (The organization’s annual budget is $50 million.)

Ms. McLachlan appears only momentarily to ask viewers to share her support for the A.S.P.C.A.

“Sarah made it possible to do in two minutes what took 30 minutes before,” said Jo Sullivan, the organization’s senior vice president for development and communications, referring to the long-form use of celebrities in the past. “She literally has changed the way we fund-raise.”