Comcast Corp. already produces movies, television shows and national and local news programs while operating theme parks and the largest pay-TV system in the U.S.

And now, with one bold stroke, the Philadelphia conglomerate could dominate the flow of information and entertainment into American homes with historically unprecedented power.

Comcast's proposed $45.2-billion takeover of Time Warner Cable would allow it to provide television, telephone and Internet service and even home security systems to nearly 30 million homes across the country. 

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The company's reach would encompass the nation's largest markets, among them Los Angeles, New York, Chicago, Philadelphia, Washington D.C. and San Francisco. By taking over Time Warner Cable's nearly 1.8 million Southern California customers, Comcast would become the region's dominant pay TV operator.

The audacious move comes just three years after Comcast took control of media giant NBCUniversal in a deal that was valued at more than $30 billion. It continues the half-century quest of Pennsylvania's Roberts family to build the nation's preeminent media company.

Six decades ago, Comcast founder Ralph J. Roberts, now 93, made a living selling suspenders and belts. But in 1963 he gambled on new technology by buying a 1,200-subscriber cable TV system in Tupelo, Miss.

Now the company controlled by his son Brian L. Roberts, 54, is hoping to build an electronic beltway into nearly a third of all homes in the U.S. with pay TV. 

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"Brian Roberts is, in fact, the John D. Rockefeller of the 21st century," Harvard Law School visiting professor Susan Crawford said Thursday. "He's cornered an essential input into every aspect of American life."

Comcast already provides coverage of the Olympics, "Sunday Night Football," auto races and NHL hockey to millions of American viewers, and the merger would extend Comcast's reach into Southern California sports with channels devoted to the Lakers and Dodgers.

A prime motivation for the merger is an onslaught of competition and more places for consumers to get their entertainment. Satellite TV giants DirecTV and Dish Network and telephone companies Verizon and AT&T all offer television and, in some cases, Internet service.

Even search giant Google Inc. has been installing high-speed data lines for broadband service in Kansas City — and has plans to add systems in Austin, Texas, and Provo, Utah — to compete with cable companies. 

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Internet streaming companies, including Netflix and, pose a threat too. They offer movies and original TV shows, and at much lower cost to customers than the traditional cable providers.

For these reasons, cable companies have been feeling squeezed and have lost some of their bargaining power when negotiating new distribution deals with programmers Walt Disney Co., 21st Century Fox, CBS Corp. and others.

Last summer, a stalemate between CBS and Time Warner Cable resulted in a monthlong service blackout to Time Warner Cable customers in Los Angeles, New York and Dallas. Time Warner Cable eventually agreed to CBS' payment terms, but the battle ultimately cost it more than 200,000 subscribers.

By adding more cable subscribers to the Comcast fold, the company hopes that it will have more purchasing power during contentious negotiations and, thus, a greater ability to push back on rising programming costs. 

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Media watchdogs and members of Congress quickly expressed concern about concentrating so much control into the hands of one company. Two ranking U.S. senators said they would convene hearings on Capitol Hill to scrutinize possible ramifications of a merger.