WASHINGTON — Senate Democrats announced on Tuesday that they were one supporter away from winning a vote to restore the so-called net neutrality rules that the Federal Communications Commission rolled back in December.

Meanwhile, the legal fight against the FCC repeal began on Tuesday, with a flurry of lawsuits filed to block the agency’s action.

North Carolina is suing along with California, Connecticut, Delaware, Hawaii, Illinois, Iowa, Kentucky, Maine, Maryland, Massachusetts, Minnesota, Mississippi, New Mexico, Oregon, Pennsylvania, Rhode Island, Vermont, Virginia and Washington as well as the District of Columbia, according to media reports.

The suit, filed by 21 state attorneys general, said the agency’s actions broke federal law. The commission’s rollback of net neutrality rules were “arbitrary and capricious,” the attorneys general said, and a reversal of the agency’s long-standing policy to prevent internet service providers from blocking or charging websites for faster delivery of content to consumers.

Mozilla, the nonprofit organization behind the Firefox web browser, said the new FCC rules would harm internet entrepreneurs who could be forced to pay fees for faster delivery of their content and services to consumers. A similar argument was made by another group that filed a suit, the Open Technology Institute, a part of a liberal think tank, the New America Foundation.

Suits were also filed on Tuesday by Free Press and Public Knowledge, two public interest groups. Four of the suits were filed in the U.S. Court of Appeals for the District of Columbia Circuit. The Free Press suit was filed in the 1st U.S. Circuit Court of Appeals.

“The repeal of net neutrality would turn internet service providers into gatekeepers — allowing them to put profits over consumers while controlling what we see, what we do, and what we say online,” said Attorney General Eric T. Schneiderman of New York, who led the suit by the state officials.

The lawsuits have long been expected. The filings on Tuesday, petitions to begin the suits, kick off what is expected to be an extended legal and political debate about the future of internet policy.

Road ahead for FCC challenge

But even if Democrats win that vote, they have a long way to go before they are able to reinstate rules that prevent internet service providers from creating fast and slow lanes for online users. Here is a look at their difficult road ahead, and some of the motivations:

What are the Senate Democrats doing?

Senate Democrats said on Tuesday that all 49 members of their caucus had agreed to sign on to a resolution that would overturn the FCC repeal of net neutrality rules. They are using a tool of the Senate, the Congressional Review Act, which requires a simple majority to overturn a recent order by a federal agency.

The Democrats also have the support of at least one Republican, Sen. Susan Collins of Maine. So that leaves them searching for one more Republican to join their effort to get the necessary 51 votes.

“Given how quickly we have gotten 50, we have a real chance of succeeding,” Sen. Chuck Schumer of New York, the Senate minority leader, said in a statement.

If this passes, are the rules automatically reinstated?

No. The House would have to pass a similar resolution, also using the Congressional Review Act, and the chances there are slim. Rep. Mike Doyle, D-Pa., is leading the effort there and has 80 Democrats on board so far. But Speaker Paul D. Ryan, R-Wis., could refuse to bring it to a vote. And 218 signatures would be needed to send it to the floor through a petition.

Finally, the president would have to sign the legislation. That, too, seems unlikely, since the White House has said it supported the FCC’s vote.

When will the Senate introduce its bill?

It could be months. Lawmakers have 60 days after the FCC puts its December order in the federal registry to introduce their resolution. The agency hasn’t done that yet and could delay the process for several days and even weeks.

If this is such a long shot, why are Democrats putting so much effort into it?

Many Democrats would like to turn net neutrality into a bigger political issue before the 2018 midterms. The efforts to overturn the FCC order are aimed to raise awareness about an issue that has broad interest, particularly among younger voters, Democratic lawmakers have said. Consumer advocacy groups like Free Press, Demand Progress and Fight for the Future, have been singling out lawmakers who have either supported the FCC order or have not spoken up in favor of restoring rules.

What are the other efforts going on around net neutrality?

There are a few major fights underway to bring back net neutrality. On Tuesday, 21 attorneys general sued to block the FCC’s repeal. The nonprofit Mozilla Foundation, the group behind Firefox web browsers, also sued the commission. More public interest groups and tech companies are also expected to take legal action. In addition, a few lawmakers have introduced bills to bring back rules.