The U.S. gun industry faced a new set of challenges to its financial and political power Tuesday as more of its Washington allies called for gun control and a major investor sought to get out of the firearms business entirely.

In Washington, a trio of new senators — all elected with National Rifle Association backing — said they were willing to discuss tightening gun laws. The White House gave a stronger signal of President Obama’s support for reinstating a ban on assault weapons.

A new law, if it should come, is still far off. In the business world, however, there was action Tuesday. Cerberus Capital Management, a huge investor in the gun industry, said it would sell its marquee gun company. Also, Dick’s Sporting Goods promised to stop selling “modern sporting rifles,” at least temporarily.

All of that would have seemed impossible a week ago, before a man with a semiautomatic rifle killed 20 students and six adults Friday at an elementary school in Newtown, Conn.

Suddenly, the debate over guns took on more ferocity. Now, even some allies of the gun industry say that weapons like those of the Connecticut shooter were looking a little less necessary.

“I don’t need a 25-round clip for effective home defense, and I sure don’t need one for hunting,” Rep. Martin Heinrich (D), a newly elected senator from New Mexico who had “A” ratings from the NRA, told a local newspaper. “That’s just too much killing power. It defies common sense.”

The NRA, which had been silent since the tragedy, released a statement Tuesday saying it had refrained from commenting out of respect for the Newtown families but is “prepared to offer meaningful contributions to help make sure this never happens again.” The organization said it will hold a news conference Friday in Washington.

On Tuesday, the fourth day since the massacre, its aftermath played out as two widely different stories.

In Newtown, it was another day for burying children. At St. Rose of Lima Roman Catholic Church, there were back-to-back funerals for James Mattioli and Jessica Rekos. Both were 6 years old.

Outside of Newtown, the tragedy seemed to have affected the country’s financial and political establishments in a way that other mass shootings had not.

Both began to focus on the weapon that gunman Adam Lanza apparently used for most of his killing. It was a .223-caliber Bushmaster semiautomatic rifle, which traces its origin to the M-16 assault rifle designed for U.S. troops in Vietnam.

The company that manufactures Bushmaster rifles, Freedom Group Inc., had been funded and assembled by Cerberus. After the shootings, Cerberus came under pressure from one of its own major investors: the California State Teachers’ Retirement System.

Late Monday, Cerberus sided with the teachers. The firm announced Tuesday it will sell its stake in Freedom Group, the nation’s largest gun manufacturer.

“It is apparent that the Sandy Hook tragedy was a watershed event that has raised the national debate on gun control to an unprecedented level,” Cerberus said in a statement. “It is not our role to take positions, or attempt to shape or influence the gun control policy debate. . . . There are, however, actions that we as a firm can take.”

Also, Dick’s Sporting Goods said it was suspending nationwide the sale of “modern sporting rifles,” a category of guns based on the same design as the Bushmaster used in Connecticut. The chain said it would pull all guns out of the store closest to Newtown “during this time of national mourning.”

And Wal-Mart removed a listing for a Bushmaster rifle from its Web site. It was not clear whether Wal-Mart was still selling the weapon in its stores. Wal-Mart did not respond to requests for comment Tuesday.

The U.S. gun industry has been one of the brightest spots in the U.S. economy in recent years, even through the recent downturn. This year, it racked up $11.7 billion in sales and $992 million in profits, according to the research firm IBISWorld.

The financial crisis and Obama’s election saw a surge in gun sales. Many buyers were either worried about rising crime during the downturn or the prospect of new gun-control rules from the Obama administration. Since 2007, the industry has grown at a 5.7 percent annual pace.

The industry produced more than 6 million guns last year — a number that has doubled over the past decade, according to a report from First Research. About half of those were handguns, with rifles making up 35 percent.

But on Tuesday, some of the biggest gun makers in the country watched the value of their shares tumble. Smith & Wesson fell 10 percent, to $7.79. Sturm, Ruger and Co. slid 7.7 percent, to $40.60.

Analyts said this reflected new fears that Congress would impose tighter regulations on guns.

In Washington, it did seem as though there was cause for worry.

At the White House, press secretary Jay Carney said that Obama was explicitly supportive of several measures demanded by gun-control groups. He listed a reinstatement of the assault-weapons ban, which expired in 2004. Sen. Dianne Feinstein (D-Calif.) promised to introduce that kind of legislation on the first day of the new Congress next month. The original ban covered 18 models of firearms, but still left many powerful weapons legal.

Carney also said that Obama supports closing a loophole that limits scrutiny of weapons sales at gun shows. This was a new level of detail about Obama’s goals for gun legislation.

“There are other elements of gun legislation that he could support,” Carney said. “People have talked about [restricting] high-capacity ammunition clips, for example, and that is something that he would certainly be interested in looking at.”

Carney’s comments came after high-profile shifts by several Democrats who have been friendly to the gun lobby in the past. On Monday, Sens. Joe Manchin (W.Va.) and Mark R. Warner (Va.) said they would be open to reinstating the assault-weapons ban. Obama called Manchin on Tuesday in a gesture of support.

There also were new calls to deal with gun control from three incoming senators who had been backed strongly by the NRA: Heinrich, Heidi Heitkamp (D-N.D.) and Joe Donnelly (D-Ind.).

And Richard J. Durbin of Illinois, a top Senate Democrat, told The Washington Post’s Greg Sargent that his party intends to offer a whole series of measures aimed at reducing gun violence early next year.

“This is likely to be part of a package of proposals,” Durbin said, in a reference to the assault-weapons ban, adding that Democrats would consider including other ideas such as limiting high-capacity magazines, beefing up background checks, expanding mental-health services, and looking at violence in movies and video games.