How dedicated is Bill Porter? This dedicated: Once, during an ice storm, the door-to-door salesman, who suffers from cerebral palsy, crawled the last part of his seven-mile route on his hands and knees. How positive and upbeat is Porter? This positive and upbeat: He describes that day—during which he also dragged his briefcase full of catalogs and order forms up his iced-over driveway—as “one of the best I ever had selling. More people were home because of the storm.”

Porter’s is one of those jaw-dropping, grit-and-gumption stories that could be a TV movie, and is: Door to Door, which will air July 14 on TNT, tells a very personal tale of quiet heroism and private victories. “Bill’s whole attitude is ‘I never did anything heroic. I had to pay the rent,’ ” says actor William H. Macy, the Fargo star who plays Porter and cowrote the script (with director Steven Schachter) after seeing a 20/20 piece on Porter. “It’s because of this stoical, can-do attitude, this indomitable spirit, that we’re allowed to cry.”

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Porter would probably prefer you didn’t. Born in San Francisco in 1932, the only child of a housewife and a salesclerk, he says he wasn’t allowed to dwell on his disability, which left his right side twisted and his speech slurred. His mother, Irene, “was always very positive,” says Porter, “and she insisted that I be the same way.” When he was 17, she enrolled him in public high school, and upon graduation his father, Ernest, insisted that he get a job—a task easier said than done. After four months of daily rejections, Porter’s employment agency told him to go home and collect welfare. So he combed the want ads himself, eventually applying for a job with Watkins, the nation’s oldest door-to-door sales company. “I had to convince them,” recalls Porter. “They gave me the worst territory, and I worked strictly on commission.” His mother would write out the word “persistence” on a slip of paper and hide it in his lunch bag.

After a year Porter began winning sales awards. Nothing could dampen his enthusiasm. When people refused to open the door or slammed it in his face, he would silently repeat the mantra “The next customer will say yes.” Many did—even if Porter had to work on them for years. “He just never takes rejection personally,” says Watkins president Mark Jacobs. “He’s relentless. He’s irresistible.”

And indomitable. Each day Porter—who lived with his mother—would wake at 4:45 a.m. and spend 90 minutes dressing himself before catching a 7:30 bus, the first of two that would take him to his west Portland, Ore., sales territory by 9. Often he wouldn’t return home until after 7 p.m. When his mother went into a nursing home in the mid-1980s (his father had died in 1962), Porter had to ask the bellhops at a downtown hotel to take over one of her tasks—buttoning his collar and attaching his clip-on tie each morning.

But Porter kept working. In 1985 he hired a young mother, Shelly Brady, to be his delivery driver and housekeeper. They soon progressed from “employer and employee to just great friends,” she says. She helped Porter cope with the loss of his mother to Alzheimer’s in 1989. Then, in 1993, after a five-month recovery from back surgery left him without any income and unable to make his mortgage payments, Brady and her husband, John, scraped together enough cash to buy his house and rent it back to him for next to nothing.

In 1998, after the 20/20 piece ran, Porter was barraged by invitations from corporations like Amway and Nike eager to have him visit as a motivational speaker. At Brady’s urging he agreed and would stand beside her while she did most of the talking. “You meet him and realize that what’s important is what’s inside of us,” says Brady, 39, whose book Ten Things I Learned from Bill Porter came out in June. “Once you hear his story it just puts everything in perspective.”

Porter says he’s happy to inspire, but selling will always be his main game. Hit by a car in 1997, he hasn’t been able to walk his beat, so he now phones his 500 regular customers from a tiny desk in his bedroom. “I can’t imagine ever retiring,” he says. “My customers are like family.” He never married (“There was a time I had a crush on someone,” he says, “but nothing ever came of it”) and still lives in his mother’s home, spending his free time watching Matlock reruns or listening to sports on the radio. Asked if he’s surprised by what he has achieved, he looks nonplussed, then replies, “It never entered my mind that I couldn’t.”