"This thing usually goes away. They don't stay focused, they don't stay after it," said Larson.

This time, Larson said, is different. "You've got a president with a bully pulpit, you've got a mid-term election; there is going to be an awful lot of heat," he said.

Larson also said he was encouraged by the president's Wednesday speech, which he said demonstrated Obama's determination and commitment — an approach different from what members of his party have come to expect.

"If there's one thing you can say about the president it's that he's persistent ... sometimes agonizingly so," Larson said, speaking of instances in which Obama has courted members on the opposite aisle just to get something done.

"Usually, no matter what, you rarely see this president angry, no matter what the circumstance is. Sometimes he'll reflect disappointment but most of the time he'll say well we've got to sit back down together," Larson said.

On the gun issue, however, Larson said: "It is permanently seared in his presidency and DNA and he will not let go."

Some of the most vocal lobbyists said they haven't even figured out what the next step is for the gun-control movement.

Sandy Hook Promise, the group that sent families to Washington to pressure legislators in the lead-up to the vote, declined to comment. A spokesman said that they need to "regroup" and that while they would be taking steps going forward, "We need to take some time to figure out what the next steps are."

Blumenthal spoke on the Senate floor Thursday, criticizing his colleagues for their failure to pass a background check expansion — a provision many supporters viewed as "common ground" early in the process. Blumenthal assured senators that the "Connecticut Effect" — a term coined by the NRA to describe a rise in support for gun control that would soon diminish — would be long-lasting.

"Do not underestimate the power of the Newtown families. They will help to hold accountable and answerable to the people of America the actions that were taken here, the votes that were cast. Votes have consequences just as elections do, and the people of America will remember," Blumenthal said.

"Our job now is to raise awareness, spread the rage that we feel, raise that rage and organize and enable and empower citizens to be heard and heeded by this body."

Several groups, some created in the aftermath of the Newtown shooting, have vowed to do the same. One, a national organization called Moms Demand Action for Gun Sense in America, models itself after Mothers Against Drunk Driving, a group that started as a grass-roots movement and over time built enough support to change laws.

"I think one thing that MADD did so well is they helped to change the culture or the perception. When MADD started out, someone used to nod their head … say oh, someone's driving tipsy," said Deborah Lewis of West Hartford, who is head of the Central Connecticut chapter of Moms Demand Action.

Like MADD, Lewis said: "We're educating and alerting people on gun violence. The gun lobby has been so powerful and preying on people's fears."

Lewis said that after the vote Wednesday, her organization saw a spike in membership, an increase in donations and record traffic on its website.

Not everyone sees MADD's success as a perfect analogy to the gun-control movement. Pinciaro said selling gun control presents challenges that opponents of drunken driving didn't face — perhaps most significantly millions of gun owners who say they are law-abiding and have the Second Amendment on their side.

One other sobering note for gun control supporters was the harsh reminder they received last week — that to compete with the powerful pro-gun lobby, money is necessary.

David Stowe, co-chair of Newtown Action Alliance, said the goal now is to make voting against gun control into something feared as much as a low NRA rating. He and others are eyeing the 2014 election cycle.

"The NRA … they've always had the money, which is now counterbalanced," said Stowe.

He cited Mayors Against Illegal Guns and Americans for Responsible Solutions, the group founded by former Arizona Congresswoman Gabrielle Giffords, who was injured in a 2011 mass shooting in Tucson.

"Look at what happened in Chicago," said Stowe, pointing to a primary election in which a pro-gun candidate bowed out after being targeted by Mayor Michael Bloomberg's Super PAC. "That money was never there before; it's there now," said Stowe, adding that "a lot of these politicians are not used to having ads" opposing those of the NRA.

"We're certainly working on looking at different races to target, different groups to coordinate with, fundraising for different campaigns coming up," Stowe said.

Stowe also said he thought Wednesday's vote could help his cause.

"In reality, what happened yesterday might work out best in the long run. … All it proved to do is energize millions and millions of people who are really angry," Stowe said Thursday.

Earlier that day, he and other members of Newtown Action Alliance had spoken with Vice President Joe Biden on a conference call. He said Biden told them that some of the senators said they wanted to vote for the measure but "they just couldn't do it for political reasons."

A Facebook post quoted Biden as saying that the senators told him: "Joe, don't ask me to walk the political plank. ... I can vote for immigration or guns, I can't do both. My constituents back home will forgive me for voting on one, but not both."

That view enrages Newtown activists and the lawmakers who have grown close to them since Dec. 14. One of them, Murphy, worried after Wednesday's Senate defeat about what it may take, realistically, to bring about meaningful gun reform.

There's going to be another massacre," he said. "These mass shootings are not decreasing in frequency; they're increasing in frequency."