Correction: A previous version of this article incorrectly described how the killers at Columbine High School acquired their weapons in 1999. They attended a gun show with a girlfriend, who as an 18-year-old was legally allowed to purchase guns; they did not buy the weapons themselves. This version has been corrected.

In the weeks after the Columbine High School massacre in 1999, Senate Democrats led the way on passing a modest gun-control bill, even though they were in the minority. The issue commanded the national spotlight for a few weeks until it was blocked by House Republicans.

Thirteen years later, and now holding a majority in the Senate, Democrats have run for political cover after a similar suburban Denver shooting. Congressional leaders have declined to endorse any legislative remedy, and the most politically endangered Democrats have either fully embraced gun rights or lamented that nothing can be done.

The hushed response to last week’s tragedy signals just how fearful Democrats have become of anything that upsets the National Rifle Association, with its vast political clout, and how even once-ardent supporters of gun control are now resigned.

Sen. Charles E. Schumer (D-N.Y.), whose landmark legislative achievement was sponsoring the now-lapsed assault weapons ban, told reporters Tuesday that there is no political path for gun legislation. He said that “the way to overcome it is for citizens, the silent majority” to create a groundswell of support for modest provisions, such as limiting the size of ammunition magazines that can be sold online.

“I don’t expect anything to happen,” Sen. Sherrod Brown (D-Ohio), who backed gun-control efforts while in the House, said Tuesday. He still supports reinstating the assault weapons ban, which lapsed in 2004 without a forceful effort to maintain it, but said there is no hope on the issue.

Sen. Jon Tester (D-Mont.) said, “You can’t stop crazy people from doing crazy stuff.” Tester earned an A grade from the NRA and is seeking its endorsement in his difficult reelection campaign.

He is emblematic of today’s Democratic Party — and is part of an effort by Schumer and other congressional leaders to appeal to rural voters. Before the 2006 midterm elections, they recruited candidates with centrist-to-conservative views on guns, including Tester, Sen. James Webb (Va.), Sen. Robert P. Casey Jr. (Pa.) and Sen. Claire McCaskill (Mo.).

The shifting views on the Hill reflect shifting views among Americans. A 2010 Gallup survey showed that support for greater gun restrictions fell 34 percentage points over 20 years, while support for fewer restrictions or the status quo grew by about the same amount.

In Colorado, many people reacted to Friday’s mass shooting by seeking to buy guns, not ban them — similar to what has happened after other recent massacres.

The number of requests for background checks of gun buyers increased noticeably after the shooting in Aurora, according to a spokeswoman for the Colorado Bureau of Investigation.

From Friday to Sunday, the agency conducted 2,887 background checks, which are required before making a legal gun purchase in Colorado. That number represents a 43 percent jump from the same stretch the previous weekend and an increase of 39 percent from the first weekend in July.

 On the Friday of the shooting, the agency processed 1,216 background checks, compared with 880 the previous Friday.

“We’ve seen some increased business since the shooting last week, I think from people wanting to protect themselves,” said Sheri Baker, co-owner of Rocky Mountain Guns and Ammo in nearby Parker.

After Friday’s shooting, four House and Senate Democrats proposed eliminating gun magazines that can fire up to 100 bullets, as the Aurora gunman reportedly attempted, and reinstating the assault weapons ban.

“The silence is deafening,” Sen. Frank R. Lautenberg (D-N.J.) told reporters Tuesday, outraged at the lack of a gun-control debate.

Senate Majority Leader Harry M. Reid (D-Nev.) suggested holding off on anything related to the shooting. “I think we should just wait for a reasonable period of time before people are off making statements what they should do and what they shouldn’t do,” he said.

In 1999, on the heels of Columbine, Senate Democrats decided to stage an immediate fight on the issue, despite holding just 45 votes. The teenage killers attended a gun show with a girlfriend, who as an 18-year-old was legally allowed to purchase guns; those shows were not covered by a 1994 law requiring background checks.

Lautenberg, with Schumer at his side, led the effort to require background checks at gun shows, offering an amendment to a broader bill dealing with juvenile crime. Republicans at first blocked the amendment but quickly retreated amid a public outcry, and on May 20, a month after the Columbine shootings, the amendment passed as Vice President Al Gore cast the tie-breaking vote. While the bill stalled later that summer, Democrats declared victory.

“We called their bluff,” Schumer gushed at a news conference afterward. “This is the most significant change in gun control since the Democrats lost the Congress in 1994. It will never be the same again. The vise lock that the NRA has had on the Senate and the House is broken.”

Brady Dennis in Colorado contributed to this report.