Yet membership has picked up this year amid a continuing rise in gun purchases, with more than 1,000 new dues-paying members signing up online every day, the group says, a surge it attributes to fears of stricter federal controls from a Democratic-led Washington.

President

Biden

said Sunday that he is prepared to call Republican senators to press for legislation that would expand background checks.

The cover of the January issue of a magazine for NRA members features a grinning Mr. Biden, with the tease, “Biden thinks he has a mandate to take away your rights.”

Elected officials who have long supported the group still do.

Mike Pompeo,

a possible Republican presidential candidate, cut an NRA video this month that begins, “I’m Mike Pompeo, fellow NRA member and former secretary of state.”

“The NRA hasn’t lost a beat,” said NRA spokesman

Andrew Arulanandam.

“The simple fact is no other organization can move the ball in Congress and move the ball in the states when it comes to continuing to improve gun rights, hunting rights and self-defense laws like the NRA. People realize that.”

John Feinblatt,

president of Everytown for Gun Safety, said he believes the gun group’s influence has waned as scandals around it have proliferated. “With the NRA preoccupied by its own survival, we have a unique opportunity to address America’s gun crisis, and we need to seize that moment,” he said.

Sen. Chris Murphy

(D., Conn.) said Sunday on NBC’s “Meet the Press” that the NRA’s internal issues have given pro-gun control lawmakers a boost of confidence. “I’ve gotten a lot of calls from Republicans in the Senate who don’t want to fight this fight any longer because the NRA’s authority is fading, the antigun violence movement’s impact is increasing.”

Other lawmakers said the NRA’s decadeslong no-compromise approach to opposing any new gun-control measures has penetrated so deeply into the Republican Party over the past few decades that lobbying on individual federal bills is less necessary.

“A weakened NRA is certainly helpful, but the gun industry writ large is still powerful. So long as the Republicans are more scared of upsetting the far-right gun lobby than they are of the American people, they will continue to oppose any reform,” said

Sen. Bob Menendez,

a New Jersey Democrat.

After a 21-year-old killed eight people at Atlanta-area spas and another 21-year-old killed 10 people at a grocery store in Boulder, Colo., Democratic lawmakers renewed their call for universal background checks and a ban of assault-style weapons. Mr. Menendez and

Rep. Barbara Lee

(D., Calif.) also reintroduced bicameral legislation that would improve the Bureau of Alcohol, Tobacco, Firearms and Explosives’ ability to access and disclose to local authorities gun records and gun-tracing data.

But the slim Democratic majority in the Senate means any of those bills—all opposed by the NRA—would likely be blocked by a Republican filibuster even if all 50 Senate Democrats supported them, which wouldn’t be a certainty. Mr. Biden is exploring executive actions that could tighten gun control but also stressed at a recent news conference that his administration has other priorities, such as infrastructure.

The renewed focus on gun control comes as the nation’s largest and oldest gun-rights group is back on its heels financially and legally. New York Attorney General

Letitia James

filed a civil lawsuit in August seeking to dissolve the organization, alleging widespread spending abuses at the nonprofit.

Arguing that it wants to escape a “corrupt political and regulatory environment” in New York, the NRA in January filed for bankruptcy protection and said it hoped to move to Texas after being domiciled in New York for its 150-year history. Hearings on key motions that will determine the course of the bankruptcy are scheduled to start April 5.

Meanwhile, the group has been racked by internal boardroom feuds since early 2019. Board members have raised questions over expenses by top officials including Chief Executive Officer

Wayne LaPierre,

who has denied wrongdoing but last year repaid the NRA about $300,000 related to allegedly excessive travel benefits.

In bankruptcy filings, the NRA reported that fundraising troubles during the pandemic fueled a revenue drop of 7% in 2020, on top of a 17% decline in 2019.

The group’s legal expenses have soared in recent years, with the NRA embroiled in civil litigation with its former ad agency, a congressional probe and the New York attorney general investigation. And the NRA has doubled down on litigation across the country to swat away state and local gun-control measures.

That has left less money for lobbying and campaign spending. “If you spend one dollar on litigation, it’s a dollar that could be spent on something else,” said NRA general counsel

John Frazer

in a recent deposition in the bankruptcy case.

Lobbying expenditures dropped from more than $5 million in each of 2017 and 2018 to $3.2 million in 2019 and $2.2 million last year, lobbying disclosure reports show.

The NRA’s spending on federal elections declined last year to $29 million from $54 million in 2016, according to the nonpartisan Center for Responsive Politics. But that is still the second-most it has ever spent in an election cycle, the data show.

At the same time, the NRA has lost ground in the Democratic Party, as reflected in shifts in its grading system of electoral candidates. Just a lone Democratic candidate for U.S. House or Senate last year had received the NRA’s “A” grade—defined by the group as “solidly pro-gun”—as of shortly before the November election, while a decade earlier more than a quarter of Democratic House or Senate candidates received A grades.

Despite the NRA’s financial woes, Republican consultants and lobbyists contend the group’s clout hasn’t taken much of a hit, because it maintains a core group of members who can be energized to vote and write politicians on gun issues.

“It’s not about the cash, it’s about the votes” the NRA can deliver to political candidates, said a lobbyist on Second Amendment issues.

Mr. LaPierre said in February at the American Conservative Union’s annual conference, also attended by former President

Donald Trump,

“You can no more kill the NRA than you can stop the sun from rising in the east.”

Write to Julie Bykowicz at julie.bykowicz@wsj.com and Mark Maremont at mark.maremont@wsj.com