Executives of Comcast and Time Warner Cable came to a Senate hearing on their merger plan Wednesday prepared to dive deep into antitrust analysis and specifics of the broadband and cable industries.

But many of the Democrats on the Senate Judiciary Committee were more interested in how the deal would affect consumers. They directed tough questions about how the creation of a mega cable and Internet service provider with poor track records on customer service could harm consumers.

"There's no doubt that Comcast is a huge, influential company with more than 100 lobbyists" hired to persuade regulators and lawmakers to approve the deal, said Sen. Al Franken (D-Minn.) "But I've also heard from over 100,000 consumers who oppose the deal."

Comcast executive vice president David Cohen said at the hearing that he couldn't promise to reduce prices on their services. The rise of cable bills at three times the rate of inflation is among the many concerns consumers have about the proposal that would merge the top two cable firms and the biggest and third-biggest broadband providers.

"What we've heard is a general sense of skepticism by my collegues, which is reflected in the general public, about how this deal will really help consumers," said Sen. Richard Blumenthal (D-Conn.). "Where's the beef? Apart from vague, potential promises of good things happening, the case has yet to be made that consumers will benefit in a tangible and substantial way."

Sen. Amy Klobuchar (D-Minn.) asked if promises to bring higher quality and faster broadband to more U.S. consumers wouldn't happen without a merger. Cohen said the deal makes it possible for Time Warner Cable and Comcast customers to more quickly get faster speeds. Cohen agreed the company needs to do a better job with customer service.

"It bothers us that we have trouble delivering real high-quality service on a consistent basis," he said, adding that Comcast has put more money into improving its services.

Franken said it is hard to trust the company's promises. When Comcast chief executive Brian Roberts testified to Congress for its merger with NBC Universal three years ago, the executive said Time Warner Cable was important competition to keep it in check. Now, Comcast argues Time Warner Cable isn't a competitor, Franken said.

"You can't have it both ways," Franken said.