Those perusing an eight-page Fortune magazine feature on J. Joe Ricketts while searching for reasons the billionaire TD Ameritrade founder has decided to plough tons of money into Republican political campaigns might find a good clue here:

Joe Ricketts actually possesses the asset that so many politicians love to claim: an up-by-the-bootstraps biography. Born in Nebraska City, Neb., to a carpenter and a homemaker, he grew up poor, with three brothers and a sister. His first job was in third grade, working as a janitor’s assistant.

After working his way through Creighton University, a Jesuit school in Omaha, Ricketts became first a credit analyst at Dun & Bradstreet (DNB), then a stockbroker. In 1975, when the SEC deregulated broker commissions, the 33-year-old Ricketts saw an opportunity. Why should investors have to rely on full-service brokers when many of them knew what they wanted to invest in anyhow? The same year, with a few partners, he opened First Omaha Securities. “No one had really brought Wall Street to Main Street,” says J. Randy MacDonald, Ameritrade’s CFO from 2000 to 2006. “The pioneers of discount brokerage were three people: Charles Schwab, Joe Ricketts, and probably Muriel Siebert.”

Ricketts’s best insight was technological. His firm was the first to execute trades using the touch-tone phone instead of a live person, in 1988. In 1995 he saw the potential of the Internet and scooped up K. Aufhauser & Co., one of the first firms to use the web for trading.

He also worked his tail off to make his company a success. The four Ricketts children — J. Peter, now 48; Tom, 47; Laura, 45; and Todd, 43 — helped out too. “We didn’t take vacations,” remembers Tom. “We stuffed envelopes on weekends, and we got paid in sugar cubes.”

Unlike some people involved in this political campaign season, then, Ricketts has firsthand knowledge of the importance of the entrepreneur to the American economy.