Reaction was swift to the proposed new rules, as consumer groups accused the commission of betraying its promise to maintain net neutrality, or equal treatment for both providers to and users of the Internet. That prompted an immediate rebuttal from the F.C.C. chairman, Tom Wheeler, who said late Wednesday that speculation that the commission was “gutting the open Internet rule” was “flat out wrong.”

The jockeying continued on Thursday. Verizon, which brought the court challenge that prompted the last set of open Internet rules to be struck down in January, issued a statement warning against “unnecessary and harmful” new rules. Consumer advocates reiterated their opposition.

Mr. Wheeler stepped up his defense of the commission’s plans. “The proposal would establish that behavior harmful to consumers or competition by limiting the openness of the Internet will not be permitted,” he wrote in a post on the F.C.C.'s blog.

The sparring will be closely watched by every company that depends, even peripherally, on the Internet — which is to say, just about every company. Businesses that use Internet connections to provide consumer services — obvious ones like Google and Netflix but also home alarm system providers, medical equipment companies and even makers of washers and dryers — will thrive or fail based on how much it costs them to maintain easy online contact with households and businesses.

As such, the lobbying ahead of the release of the proposed new rules on May 15 is certain to be intense. As recently as Tuesday, officials from the National Cable and Telecommunications Association, which represents cable and broadband companies and is led by Michael K. Powell, a former F.C.C. chairman, met with commission staff members to discuss the pending proposals.