The Federal Communications Commission on Thursday voted along party lines to approve a proposal to explore subsidizing broadband Internet for poor Americans. The plan, introduced last month by the agency’s Democratic chairman, Tom Wheeler, helps pave the way for sweeping changes to a $1.7 billion phone subsidy program.

Republicans have opposed extending the phone subsidy — known as Lifeline and initiated in 1985 under President Reagan — pointing to past instances of fraud in the program and suggesting that any expansion would generate more fraud. On Thursday, the two Republican commissioners delivered strongly-worded dissents.

“Adequate controls and deterrents against waste, fraud and abuse should be in place before considering expanding the program to broadband,” said Michael O’Rielly, a Republican commissioner.

Part of Mr. Wheeler’s plan approved on Thursday was an effort to allay those concerns. In its vote, the commission adopted stricter measures to ensure eligible households claim only one subsidy of $9.25 a month. Those antifraud measures — including new record-keeping requirements for service providers, who are charged with verifying a person’s income — are expected to take effect this summer.

“I am befuddled at how this Republican program has suddenly become so partisan,” Mr. Wheeler said in responding to the dissents on Thursday. “But I am proud to cast my vote with the majority.”

The commission will now begin to discuss the logistics of how exactly to incorporate broadband into the program and write specific rules. Those changes would need to be approved by a separate vote, one not expected for at least several months.

A principal question that regulators must address is how far, exactly, the current subsidy, $9.25 a month, can go in financing broadband.

Republicans and Democrats alike have wondered about the economic feasibility of offering a mix of phone service and broadband at the same price, which Mr. Wheeler has suggested would be possible. On Thursday, both Mr. O’Rielly and his fellow Republican commissioner, Ajit Pai, said they wanted to establish a firm budget and spending cap on the program to keep its cost from multiplying. Mr. Wheeler called those concerns “a rhetorical snowstorm to distract” from the basic premise of the proposal.

Still, Democrats celebrated the significance of taking aim at the so-called digital divide, the social and economic gap between those with access to technology and those without it. Jessica Rosenworcel, a Democratic commissioner, on Thursday called a broadband subsidy essential to bridging the “homework gap” in particular, pointing to children’s increasing need for Internet access.

“Students who lack regular broadband access are struggling to keep up,” she said, noting that as many as 7 in 10 teachers assign homework that requires online connectivity. “Now is not a moment too soon, because this is about the future.”

The proposal, Mr. Wheeler said, was about attacking problems in America that the commission should be united against.

“Both political parties now engaged in serious campaigning as to who’s going to be responsible for the country and the commission in a few years,” he said. “But both political parties are in violent agreement that our country is challenged by economic inequality.”