A clutch of public interest groups, unions and media companies including Dish Network and Glenn Beck’s TheBlaze have formed the “Stop Mega Comcast” coalition to advocate against federal approval of the $45 billion cable merger.

The group spearheaded by the non-profit org Public Knowledge said it would focus on blocking the union of the nation’s two largest cable operators outright because “no set of conditions can address the substantial harms that will be caused by the merger.” The strident opposition to the merger by the coalition members is nothing new, but the Stop Mega Comcast forum may amplify their arguments at a time when there’s growing speculation about the possibility that regulators will reject the deal.

In announcing the effort, the group listed familiar concerns about the merger, including the fact that the combined company would control nearly 50% of the broadband service in the U.S. — although Comcast maintains the figure is 35%. Broadband is a hot button for regulators at a time when the FCC is evaluating its net neutrality policies. Comcast has said it would abide by the FCC’s net neutrality rules that were put in place several years ago, even though a federal appeals court struck them down in January.

Comcast described the coalition as comprised of “self-interested opponents” with competitive motivations for seeking to block the merger.

“Hundreds of community organizations, programmers, lawmakers and diversity groups have praised the pro-consumer benefits of this transaction. It is no secret that some companies that want billions of dollars in higher fees for consumers are paying lobbying firms to organize against this transaction,” said Sena Fitzmaurice, Comcast’s VP of government communications. “This minority of self-interested opponents has used the same tactics in our past deals, and their claims were not found to be credible by the expert agencies. We believe the same will be true here.”

The Writers Guild of America West is among the industry orgs in the coalition, along with the Consumer Federation of America, Greenlining Institute, Parents Television Council, Sports Fan Coalition, WeatherNation TV, FairPoint Communications, Future of Music Coalition, Hargray Communications and NTCA–The Rural Broadband Association.

In a conference call with reporters, execs with the various orgs emphasized that the combined Comcast-TW Cable would have a dangerous amount of “gatekeeper” control over aspects of the media and entertainment marketplace. They pointed to Comcast’s track record in fighting a condition of its 2011 NBCUniversal takeover — the stipulation that it carry Bloomberg TV in the same “neighborhood” as its own biz channel CNBC — as a sign that conditions would not be strong enough to police the company’s power.

Ellen Stutzman of the WGA West said flatly that Comcast, through its cable and studio divisions, would have “unprecedented” power over programming, which would ultimately mean that “writers would have fewer outlets to sell to, and they’d be paid less to create and innovate.”

The group has launched a website and plans to meet with officials at the FCC and Justice Department as they hunker down on the review of the merger, which was unveiled in February. Gene Kimmelman, prexy-CEO of Public Knowledge, also noted that they feel momentum is on their side as in the past few months there has been growing speculation that the deal will be nixed entirely or saddled with so many conditions that it becomes unattractive to Comcast.

“The conversation has been different in the last month or two,” Kimmelman said. “The concerns we want to raise could fall on receptive ears at the enforcement agencies.”

Lynne Costantini of TheBlaze said the nature of the questions that have been asked of merger opponents by FCC and Justice Dept. staffers indicates that they are grappling with the issues raised by the size and scope of Comcast post-merger. “This is not a run-of-the-mill review. They’re thinking about this in new and different ways,” she said.

The coalition cited Comcast’s overwhelming market share in the traditional cable biz as well as its size as a programmer through NBCUniversal. Other areas of concern cited were the sway that the enlarged Comcast would have to provide the broadband for connected consumer devices; the market share it would command in local cable advertising; and the impact of its size in markets with high concentrations of minority viewers.

The org’s media strategy is being handled by D.C.-based Glover Park Group, the communications firm known for its work on politically charged issues and regulatory fights such as Comcast’s 2011 acquisition of NBCUniversal.