The Virginia Senate killed legislation Wednesday that would have required private sellers at gun shows to run background checks on buyers after the bill's sponsor refused to allow it to be weakened.

Senators shot down the bill on Tuesday, but then resurrected it, saying that changing it some could garner the three votes needed to pass it out of the Senate for the first time. The bill, which is proposed annually, usually dies before it even gets to the Senate floor.

This time around, without discussion, senators killed the bill 21-19. The only vote to change was that of Sen. Charles J. Colgan, Manassas Democrat, who favored the bill, but accidentally voted against it on Tuesday.

Sen. Henry Marsh, Richmond Democrat, said he would rather face defeat with the original bill than to water it down so much that it would do nothing to prevent felons, terrorists and the mentally ill from buying guns.

"This issue is too important to risk the lives of the people of Virginia," Mr. Marsh said after the vote. "I'd rather come back when I can get a good bill, rather than something that doesn't mean anything."

The bill targeted the so-called "gun-show loophole," where private sellers at the public events are not required to conduct the background checks that licensed dealers must perform.

State Sen. Henry Marsh, Richmond Democrat, confers with Sen. Janet D. Howell, Fairfax Democrat, on legislation to require gun shows to run background checks on purchasers, prior to its defeat.

It would have required checks on everyone except those who already have a permit to carry a concealed weapon or those purchasing antique guns.

At least two senators planned to offer amendments that would have allowed private sellers to ask for a background check but would not have required it.

Mr. Marsh said the General Assembly doesn't usually make it voluntary to obey laws such as doing drugs or driving recklessly, and that it shouldn't with something as important as buying a gun.

Gov. Tim Kaine, a Democrat, said he likely would not support any bill that made the checks voluntary.

"There isn't any reason why somebody who's dangerously mentally ill or a felon should be able to get a gun under any circumstances in this commonwealth," Mr. Kaine said. "I continue to be surprised that people feel like that is OK."

Another amendment that Mr. Marsh said likely would have been proposed would have exempted rifles and shotguns from the required checks. While that may have appeased hunters, Mr. Marsh said it would have done nothing to stop those with bad intentions from getting the high-powered weapons.

"It doesn't matter to a parent or a spouse of someone who is dead or wounded what kind of gun was used," he said.

Andrew Goddard said he committed to pursuing harsher gun laws as he sat beside son Colin's hospital bed and watched him bleed from being shot four times by a student gunman at Virginia Tech. His son survived the 2007 massacre that killed 32 people and injured dozens more. The gunman's weapons were purchased legally, but not at a gun show.

Mr. Goddard said he and other families of shooting victims would continue to fight for stricter gun laws, including closing the "loophole."

"We're not anti-gun people, but we have seen what happens when a gun is in the wrong hands and we don't want that to happen again," he said.