Absent from the FCC docket early Monday evening was criticism by big entertainment companies such as the Walt Disney Co.
Netflix, the online streaming service, was expected to file comments late Monday opposing the transaction.
The deadline to file was midnight.
Both sides - those that support Comcast and those that oppose the giant cable-TV company's proposed transaction to get even bigger - attempted to control the discussion in Washington on Monday as regulators bear down on their investigation into potential public benefits and economic harms.
Comcast, which spends millions of dollars annually lobbying in Washington, announced the complex deal for Time Warner Cable in February and then agreed to divest itself of millions of TV and Internet subscribers to placate the FCC and Justice Department regulators.
Even after these divestitures, Comcast's cable systems would serve 75.4 million homes, 68 percent of all those in the United States, according to a filing Monday by the telecommunications trade association Comptel. Comptel petitioned the FCC to reject the deal.
The FCC last week requested voluminous information on Comcast's cable systems and the communities it serves as part of its investigation.
"Online video competition is the last and only hope of breaking the stranglehold of cable," the Consumer Federation of America, made up of consumer groups, told the FCC in comments that opposed the transaction and were filed Monday.
"The suggestion that there is no consumer harm here is rubbish," said Mark Cooper, the federation's research director.
Comcast does not have to respond publicly to its critics until Sept. 23. On the company's website Monday, executive vice president David L. Cohen outlined what he wrote were the benefits of the deal and the broad political support expressed in the FCC docket over the last 45 days.
The Pennsylvania State Mayors' Association supports the proposed transaction, and Mayor Nutter has organized a group of about 50 mayors who say the transaction would be good for their communities.
Gov. Corbett wrote to the FCC that "in Pennsylvania, Comcast is a tremendous corporate citizen, and I am confident this transaction will spur new economic growth and strengthen Comcast's commitment to our communities."
Maryland Gov. Martin O'Malley cited Comcast's community day of service and its Internet Essentials discounted-Internet service program for his support in the FCC docket.
Cohen wrote: "As we've said from the outset, we believe this is an approvable transaction, and we expect to agree with regulators on conditions that will further enhance the public interest while not being unduly burdensome on our business or consumers."