Advocates of stricter gun laws vowed Thursday to be louder and more passionate in the weeks and months ahead than gun-rights activists, who helped quash proposals to reduce gun violence this week that were widely popular among the public.

Working with a committed White House, gun control proponents said they are mobilizing on two fronts. In the short term, they will attempt to shame opposing senators and stoke enough public outcry in their home states to force them to switch positions.

If that fails, they said, their long-term strategy is to help elect new ones.

“They clearly had a calculation that the other side had more passion and staying power. We’re going to show them that they’re wrong,” said Jon Carson, executive director of Organizing for Action, which advocates for President Obama’s policy agenda but says it will not get involved in elections.

But the White House and its allies also conceded that they see no easy path ahead after Wednesday’s defeat in the Senate, where 46 senators voted to block a compromise that would have extended background checks to all commercial gun sales.

“There aren’t any immediate options,” said Matt Bennett, a senior vice president at Third Way, a centrist think tank that works with the White House on gun issues. “All of us are going to be searching for some kind of element that could change the dynamic enough to attract that handful of votes that we need, and we don’t know what that is yet.”

On Thursday afternoon, Senate Majority Leader Harry M. Reid (D-Nev.) pulled the gun bill, saying the Senate would “take a pause” and asserting that “this fight is just beginning.”

For now, however, the fight will continue outside of Washington.

At the White House, officials said Obama and Vice President Biden will stay vocal on the issue and do whatever they can administratively. During a conference call Thursday, Biden strategized with gun-control advocates over how to create a grass-roots movement more powerful than the National Rifle Association.

Organzing for Action, which grew out of Obama’s reelection campaign, is planning dozens of events this weekend in key states and is urging its network of supporters to pepper senators’ offices with letters, tweets and calls.

Meanwhile, Americans for Responsible Solutions, a group started by former congresswoman Gabrielle Giffords and her astronaut husband, Mark Kelly, is preparing to air television advertisements thanking four senators — Susan Collins (R-Maine), Mary Landrieu (D-La.), Kay Hagan (D-N.C.) and John McCain (R-Ariz.) — who voted for background checks.

The Giffords group also plans to air ads against senators who voted no. “It’s a target-rich environment,” Kelly told reporters.

Sen. Chris Murphy (D-Conn.) said, “The NRA doesn’t operate in a vacuum any longer, and we’re going to see that on the airwaves over the next several months. We don’t have to wait until 2014 to litigate this vote.”

Polls show nine in 10 Americans support expanded background checks, but most of the opposing senators face no immediate political threat. Many up for reelection in 2014 are entrenched incumbents in ruby-red states. And those who come from more moderate states where their votes might harm them — such as Florida, Ohio, New Hampshire and Arizona — won’t stand for reelection until 2016 or 2018.

“That’s the beauty of a six-year term,” Sen. Jeff Flake (R-Ariz.) told the Los Angeles Times.

Democrats are also being targeted. Carson said OFA will direct its resources at both Democrats and Republicans who blocked background checks. And the Progressive Change Campaign Committee is spending more than $100,000 on full-page newspaper advertisements in the home states of the four Democrats who voted no: Sens. Mark Pryor (Ark.), Mark Begich (Alaska), Max Baucus (Mont.) and Heidi Heitkamp (N.D.).

The four, who rely heavily on contributions from more liberal states like New York and California, also could face a backlash from donors.

Minnesota financial adviser Louis W. Frillman and his wife gave maximum donations to Heitkamp in her 2012 campaign. But Frillman said in an interview that he would have to “think carefully” about supporting her again.

“You can’t ignore a vote like this,” Frillman said. “People that have political power tend to be people who speak their minds and they stick with a belief system. In this case, we’ve got a number of people who appear to have bent their vote to political considerations rather than listening to what’s going on with America.”

Heitkamp’s office did not respond to a request for comment.

Murphy, who has been in the spotlight as a defender of the Newtown families, warned that “senators are going to repeatedly have to answer for their position on guns because this isn’t the last time that somebody’s going to walk into a crowded place with an AR-15.”

Advocates concluded this week that to be successful they will have to demonstrate more passion than NRA members. Wednesday’s resounding defeat may actually help them achieve that, some said.

“When people understand their senator voted against expanding background checks to cover all commercial sales, to cover things like buying guns over the Internet, they’re outraged,” Carson said. “People who we hadn’t heard from are now coming to us saying, ‘How do I sign up?’”

Ed O’Keefe and Tom Hamburger contributed to this report.

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