Majority Democrats at the agency are expected to vote Thursday to approve FCC Chairman Tom Wheeler’s net neutrality plan, which will regulate broadband like a public utility to ensure all Web traffic is treated equally. They’re also poised to encourage towns and cities to compete with the dominant telecom companies in providing Internet service to consumers.

Taken together, the two moves, which are vehemently opposed by the FCC’s two Republican members, represent a seismic shift in the relationship between the government and the companies that run the Internet — and mark the biggest change to communications policy since the 1996 Telecom Act.

“It’s a watershed change,” said Tim Wu, a Columbia Law School professor who’s been deeply involved in the debate and coined the term “net neutrality.” “The chairman is going big, and he’s basically resetting the board on broadband in this country and how the government thinks about it.”

Wheeler’s net neutrality plan will ban Internet service providers from blocking or slowing Web traffic or charging companies for online “fast lanes.” The chairman says it creates a referee for the rapidly growing Internet sector. The rules — which are endorsed by President Barack Obama — will apply to both land-based and wireless networks and to “interconnection” points between networks deep inside the Web.

Republicans and the major telecoms have slammed the rules, saying they will burden industry and chill investment. AT&T has already threatened a legal challenge — and says the industry will likely ask a court to halt the order before it takes effect.

The FCC’s other move Thursday could have an equally profound effect on the broadband market. Responding to petitions from Chattanooga, Tenn., and Wilson, N.C., the agency is expected to override state laws that restrict community-run broadband networks from expanding their geographic reach. By taking the action, the commission will send a strong signal that it supports local government broadband projects — which are sprouting up all over the country — as a new form of competition for incumbent cable giants.

Telecoms are clearly aware of the threat, with companies like AT&T pushing for state legislation that restricts city-run networks. Republicans in Congress, meantime, have warned the FCC against any unconstitutional meddling in state affairs.

“All this combined causes a paradigm shift in communications regulation,” said Robert McDowell, a former GOP FCC commissioner who stepped down in 2013 before Wheeler took the helm. “The FCC is expanding its jurisdiction, not only into network operations of the Internet but all the way to the backbone, which is a place no one thought the FCC would go a year ago.”

Wheeler made some late-stage revisions to his net neutrality plan after Google and public interest groups pressed for the changes, according to FCC sources. The search giant and advocates warned that some of the language in the plan could unintentionally allow Internet service providers to charge websites for sending content to consumers — a scenario that could result in an avalanche of fees for many Web companies.

The revisions addressed the concerns, according to the sources. The changes, however, do not appear to alter the main thrust of Wheeler’s proposed order and its utility-style regulation of broadband.

Along with net neutrality and protection of community-run networks, the FCC has been laying the groundwork for its Internet vision in other ways.

Last month, the commission, on a party line vote, approved a new official definition of “broadband,” increasing the threshold to 25 megabits per second for downloads from the previous 4 megabits. The agency called the old standard inadequate to evaluate high-speed Internet service, which today has to support a flood of data, voice services and video.

Wheeler declined to comment before Thursday’s vote, but he told the Silicon Flatirons event recently that the FCC is in the midst of “historic decisions.”

“If broadband is too slow, if it does not reach enough people, if there are not competitive choices, there are consequences for the Net, for sure,” he said, adding. “Broadband networks must be fast. Broadband networks must be fair. Broadband networks must be open.”