Continued from page 1

To underscore the weight of the issue, Vice President Joseph R. Biden presided over the vote, and families of gun-violence victims watched from the public viewing galleries.

“Shame on you,” a survivor of the 2011 Tucson shootings shouted at senators after the vote was announced.

Gun rights supporters did suffer losses, though. The Senate rejected an amendment to allow those with concealed-carry permits to carry their weapons across state lines.

Still, the background check amendment was the chief showdown.

Its defeat dooms what had become the “sweet spot” of gun legislation, as co-sponsor Sen. Charles E. Schumer, New York Democrat, described enhanced background checks, but creates significant logistical problems for broader gun measures.

Despite the setback, Mr. Reid said Democrats will try again.

“We have not given up,” he said. “I am going to do everything I can to fight for meaningful background check legislation.”

The underlying gun control bill Democrats wrote includes language intended to crack down on gun trafficking and straw purchases, as well as funding for school safety provisions. But it also includes even stiffer background checks, written by Mr. Schumer.

The Manchin-Toomey amendment was designed to replace the Schumer language, but now that chance is gone and the entire bill is threatened.

The Senate is scheduled to consider two amendments to the underlying bill Thursday. One would penalize states and local governments that release certain information about gun owners and victims of domestic violence, and the other would reauthorize and bolster programs on mental health and substance abuse disorders.

In 2004, the last time the Senate debated a major gun bill, the same situation occurred. Republicans wrote a bill to shield manufacturers from liability for gun crimes, but Democrats managed to attach amendments banning some semi-automatic weapons.

Neither side could stomach the final product, and 90 senators voted to kill it.

Dave Boyer contributed to this report.