And she is in good company. “Making fun of that reporter was just not only in bad taste, it just demonstrated the character of him,” said Christine Griffin, a lawyer and disability policy advocate in Boston. “The disability community is very upset by that, but if you look at the poll numbers, so is the rest of society.”
Mrs. Clinton’s team did not entirely hold its fire on Wednesday. Hours after she left the stage, her campaign held a conference call in which supporters condemned Mr. Trump’s mocking of Mr. Kovaleski. “You’d have to go back 50 years or more to find someone who would actually think that way,” said Tom Harkin, the former Iowa senator who introduced the Americans With Disabilities Act of 1990.
The campaign also featured the infamous clip of Mr. Trump in a new ad starring Anastasia Somoza, a disability rights advocate who was born with cerebral palsy and has known Mrs. Clinton since she was 9.
People with disabilities make up a potentially potent political coalition: A study this month from two Rutgers professors projected that more than 35 million people with disabilities would be eligible to vote this year — roughly one-sixth of the electorate. More than a quarter of the electorate either has a disability or shares a household with someone who does, the study estimated. And they are represented fairly equally in both parties. As the Republican vice-presidential nominee in 2008, Gov. Sarah Palin of Alaska spoke often of championing children with special needs, noting her own child with Down syndrome.
Jennifer Laszlo Mizrahi, the president of RespectAbility, an advocacy group, said the election had focused attention on issues affecting disabled voters as never before, with Mr. Trump’s behavior serving as a galvanizing force.
“I don’t think there’s a person with a disability on the planet who has never been made fun of,” said Ms. Mizrahi, who has dyslexia and is raising a child with physical disabilities. “Every person with a disability knows what it’s like to live with stigma.”
Ms. Mizrahi also lamented that Mr. Trump had often “conflated the word ‘stupid’ with the word ‘loser,’ ” as she put it, warning that such thinking could hinder the job prospects of people with intellectual disabilities.
On Wednesday, Mrs. Clinton did not go there, infusing her half-hour address with the earnest zeal that she tends to summon more readily during policy speeches than in campaign rallies.
She ticked off statistics, noting that nearly one in five Americans lives with a disability, and strayed from her prepared remarks — “I want you to hear this because this is not well known,” she interjected at one point — to urge people to listen.
She spoke of her own policy agenda for people with disabilities, which includes a program aimed at helping people with autism and a pledge to eliminate the “subminimum wage” paid to some people with disabilities, which she called “a vestige from an ugly, ignorant past.”
Mrs. Clinton said she had taken to carrying a copy of a recent article in The Boston Globe that detailed the successful three-decade career of a McDonald’s employee with Down syndrome.
And she described what she viewed as the “ultimate test” of a society: “how we treat our fellow human beings, especially the most vulnerable among us.”
The closest she came to mentioning Mr. Trump was at the end, when she repeated a common campaign refrain: “Love trumps hate.”
Solidifying the disabled as a voting bloc may require extra diligence, given issues of accessibility at many polling places. The Help America Vote Act of 2002 sought to remove impediments, but advocates say many barriers remain. The National Disabilities Rights Network, for one, seeks to inspect polling locations in advance, but many are not open until Election Day, making that impossible.
Until then, Mrs. Clinton seems likely to return to the theme often. Some of her most affecting moments on the campaign trail have come when people have approached her on rope lines or during round-table discussions about their struggles caring for disabled family members, and she has often turned to the subject spontaneously.
The crowd on Wednesday appeared grateful for the consistent attention.
In lieu of a sign, Geannie Bastian, 35, who uses a wheelchair, held up her college degree, saying it represented Mrs. Clinton’s commitment to improving educational opportunities for disabled people.
She said Mrs. Clinton was wise not to discuss Mr. Trump in the room. Everyone, she said, knew his record well.
“I know what that gesture is,” she said, recalling Mr. Trump’s imitation of Mr. Kovaleski. “I’ve had kids do this my entire life.”