WASHINGTON - When Comcast made its move to buy NBCUniversal, more than two dozen letters from Congress - including one from 22 Republicans - landed at the Federal Communication Commission early in its review.

Dozens more, from key chairmen and rank-and-file members of both parties, arrived before that deal was approved in 2011. The vast majority supported the merger, including one signed by 97 House members and several from minority lawmakers who hailed Comcast's commitment to diversity.

But as the Philadelphia giant now pushes a merger with Time Warner Cable, Comcast has had little congressional support, and almost none outside its home state.

Meanwhile, more than 50 black, Hispanic, and Asian members of Congress have expressed concerns about the impact of this deal and others, warning in a letter to the FCC that recent media "mega-mergers" show that "even the most reasonable conditions and diversity pledges" have proved difficult to enforce.

The lack of vocal Capitol Hill support for the merger doesn't necessarily signal opposition - few lawmakers have called for killing the deal - and Congress doesn't vote on it. That's up to the FCC and the Justice Department.

But the relative silence has encouraged critics of the proposal, and it comes as some analysts are raising concerns about its fate.

"There's a widespread sentiment that the prospects for approval of the merger have decreased over the past year," said Kevin Werbach, a University of Pennsylvania associate professor and former FCC adviser.

Recent FCC moves on Internet regulation, though separate from the merger, may signal an increasingly aggressive stance on Internet competition and concerns over the power of big companies, he said. Werbach, who sits on the board of Public Knowledge, a public interest group that opposes the deal, says the odds of approval have now slipped to about 50-50.

Comcast officials warn not to read too much into the disparity in congressional letters.

The NBC purchase was more complex, they say. It involved a cable company branching into new businesses, rather than just acquiring a peer, and led to twice as many congressional hearings, Comcast spokeswoman Sena Fitzmaurice said.

Buying a national network like NBC affected every TV viewer and congressional district, Fitzmaurice said.

By contrast, if her company acquires Time Warner Cable, millions who already have Comcast will still be served by the same company - just a bigger version.

"The deals are completely different," she said.

One industry analyst has put the odds of federal approval at just 30 percent; others still think the deal is more likely to be approved than rejected.

But confidence has fallen.

Paul Glenchur of the Potomac Research Group said he expected approval with significant conditions attached. The Justice Department, which reviews the plan on antitrust grounds, would face a high bar for blocking the merger, he said.

"You've got to prove it before a federal judge," he said. "It's not a simple, 'We don't like it, goodbye.' "

Comcast's critics, however, have been heartened that the company hasn't built a drumbeat of political support, despite its massive lobbying operation.

"Comcast is running into more trouble than they had anticipated," said Gene Kimmelman, president of Public Knowledge, which has joined the Stop Mega Comcast coalition. "It's an interestingly high level of silence."

Jeff Blum, a senior lawyer for rival Dish Network, said "significant" opposition to the deal was why members of Congress were slow to support it.

Dish and Netflix, along with consumer groups, have mounted an aggressive campaign, hiring a top-end public relations firm and two lobbyists with close ties to key lawmakers and committees.

One Senate Democrat who has stayed out of the fray received around 2,000 calls, e-mails, and letters of opposition, said an aide who asked for anonymity to discuss internal thinking.

The main congressional support for the deal has largely come from Comcast's backyard: Pennsylvania Sens. Bob Casey, a Democrat, and Pat Toomey, a Republican, wrote the FCC in support of the deal in December. On Friday, 14 of Pennsylvania's 18 congressmen sent a letter praising the deal for consumers and the economy.

"Any business in my city that is going to be able to expand, I'm certainly going to help them," said Rep. Bob Brady (D., Pa.), who led the effort.

The only other federal lawmaker to write in support so far has been Sen. Orrin Hatch (R., Utah), according to FCC records.

Comcast officials note there is still time before the FCC's informal deadline.

By a similar point during the FCC review of the NBC merger, more than 40 letters from federal lawmakers - mostly supportive - had poured in. This time, only about a dozen congressional letters have arrived. Several raised sharp questions, though only a few asked officials to block the proposal.

One opponent who didn't send a letter, Rep. Tony Cardenas (D., Calif.) said publicly last month the merger would "lead to less diverse content" and more expensive cable and Internet service.

Comcast has said that it lived up to its pledges to promote diversity, and that scores of minority civic and business groups had endorsed its record.

More than 150 governors, mayors, municipal council members, and state legislators nationwide also support the deal, according to a list touted on Comcast's website. One from Missouri wrote that when she heard about the merger, "my first thought was how quickly can this be completed?"

The FCC and Justice Department are supposed to make decisions free of politics, and a recent deal between AT&T and T-Mobile was blocked despite significant Capitol Hill backing.

Still, Comcast has sought support and tried to neutralize opposition.

Aides to two congressional Democrats who signaled they would be unlikely to support the deal said the company's lobbyists asked that they at least not attack it. Neither has. The aides would discuss their offices' private meetings only on condition of anonymity.

Republicans on the committees overseeing technology and communications said lawmakers wanted to leave the process in the hands of the agencies in charge.

"Everybody's kind of keeping their powder dry and letting the process play itself out," said Sen. John Thune (R., S.D.), chair of the Senate Commerce Committee. But, he said, "Participants and players, yeah, would like to have support." 

@JonathanTamari