Update: On Friday afternoon, Wyden and Markey withdrew their holds. A spokesperson for Markey's office said the senator and Rosenworcel had had "positive conversations" Thursday night and there is a "shared commitment to continue working" on the outstanding items on the FCC's agenda. A spokesperson for Rosenworcel declined to comment. The withdrawals were first reported by Morning Consult.

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Two top Senate lawmakers are blocking the confirmation of a Democratic official to the Federal Communications Commission, ending months of speculation about the official's fate and all but ensuring a stalemate at the nation's top telecom and cable regulator as it heads into 2017.

The decision Thursday by Sens. Ed Markey (D-Mass.) and Ron Wyden (D-Ore.) to place a hold on FCC Commissioner Jessica Rosenworcel also signals a shift by some Democrats to favor more outspoken advocates of consumer protection, aides and analysts say, particularly as Republican opponents of regulation prepare to take over the agency and roll back some of its most significant policies of the past several years, including net neutrality.

Other proposed policies, such as an attempt to end a longstanding requirement by the cable industry that customers lease set-top boxes for a monthly fee, never came to fruition. Some proponents of the regulation privately blamed Rosenworcel for not supporting the measure as wholeheartedly as her fellow Democrats at the FCC.

Markey "wants an FCC commissioner who is unequivocally committed to pro-consumer, pro-competition policies," said a spokesperson for Markey. "Recent actions from Commissioner Rosenworcel have called that commitment into question."

Without the necessary three "yes" votes for the rules, FCC Chairman Tom Wheeler postponed the set-top box vote in October, saying he hoped to approve the deal before year's end. But on Thursday, Wheeler bowed to congressional Republicans who urged him not to pursue any controversial or partisan policies in light of the presidential transition of power. Although the set-top box proposal remains on "circulation" and could technically be voted upon at any time, Wheeler's move suggests it will not see a return.

A spokesperson for Rosenworcel declined to comment.

Rosenworcel will be forced to step down from the commission by year's end if Congress does not confirm her renomination. That would leave Wheeler and the agency's other Democrat, Commissioner Mignon Clyburn, deadlocked with two Republicans, Commissioners Ajit Pai and Michael O'Rielly.

Wheeler is expected to resign as chairman to allow President-elect Donald Trump the chance to nominate his own, conservative chairman. But Wheeler told reporters Thursday that he had not picked a departure date.

As the Democrat who shepherded through some of the 21st century's most sweeping regulations for Internet providers, Wheeler could be a thorn in the side of a Republican-held FCC looking to undo his biggest accomplishments. Wheeler's term does not expire until 2018; if he were to remain a commissioner, he could vote against Republican measures and organize opposition to conservative proposals.

"If somebody wants to come in and take away a fast, fair and open Internet, take away consumer privacy, take away access for schools, libraries, low-income [consumers] and walk away from competition, I think there are serious consequences for that," Wheeler said.

But playing tough could have consequences under a Trump administration, warned Berin Szoka, president of the right-leaning think tank TechFreedom. Although the FCC is traditionally made up of three commissioners from the president's party and two from the opposition party, the White House does not have to let the opposition party — in this case, the Democrats — pick the minority members of the FCC, said Szoka.

"All the statute says is, no more than three members of any independent commission shall be members of the president's party," he said. "Bill Clinton picked the Republican seats himself and if Trump wanted to play hardball, you can see him doing the same thing."

Consumer advocates said Markey's hold was a sign that Democrats are confronting the new reality of a government that is completely controlled by Republicans.

"Jessica's been an excellent substantive commissioner, but this may be a moment when the Democrats want really aggressive fighters for their principles," said Gene Kimmelman, president of the consumer group Public Knowledge. "It's a different environment, and you may need different kinds of people."