WASHINGTON —The congressional effort to expand criminal background checks — the only form of gun control that was still on life support — received support from U.S. Sen. Mary Landrieu, but was still soundly defeated Wednesday on the Senate floor.

The measure to expand criminal background checks on commercial gun sales received 54 Senate votes in favor with 46 senators opposed, but fell short of the needed 60 votes.

Other broader proposals such as banning some assault weapons and limiting the number of bullets in ammunition clips also failed.

The defeated proposal by Sens. Pat Toomey, R-Pa., and Joe Manchin, D-W.Va., would have expanded criminal background checks to cover all commercial and online gun sales and ended the so-called gun show “loophole” of buying guns at events without proper checks.

The proposal would have exempted background checks on unadvertised private transfers of weapons, including among family members.

The legislation banned creating any kind of federal gun registry.

Sen. David Vitter, R-La., voted against the background checks and other efforts to toughen gun control as expected, although he did support a failed Republican substitute plan. He did not respond to interview requests on the topic for the second straight week.

Landrieu, D-La. and who faces re-election next year, voted for the background checks although Republicans may use it against her. She opposed the assault weapons ban and ammunition limits though. She also voted in favor of loosening gun control on a failed Republican proposal to allow national reciprocity on concealed carry handgun permits.

“The Manchin-Toomey compromise was a hard-fought but balanced approach that would reduce gun violence and make it much harder for criminals and mentally ill individuals to access guns,” Landrieu said in a prepared statement after declining an interview request. “Currently, guns can be purchased online and at gun shows without any background check whatsoever, leaving a gaping hole in our gun protection system.”

Three Democratic senators facing re-election next year — U.S. Sens. Max Baucus, of Montana; Mark Begich, of Alaska; and Mark Pryor, of Arkansas — opposed the expanded background checks. Apart from Toomey, Republicans Susan Collins, of Maine, Mark Kirk, of Illinois, and John McCain, of Arizona, voted for it.

The National Rifle Association lobbied strongly against the expanded background checks.

Critics argued that the expanded backgrounds checks added cumbersome paperwork and potential fees, while creating a potential slippery slope and taking away the focus from better enforcing existing laws.

Some families of victims from the Newtown, Conn., school shootings and from last year’s Aurora, Colo., movie theater killings were on hand Wednesday.

Former U.S. Rep. Gabrielle Giffords, D-Ariz., who was shot in the head in 2011, also was present in the effort to support the failed gun control measures.

Sandy Phillips, whose family is from Baton Rouge and whose husband hails from Lake Charles, is the mother of Jessica Ghawi, who was killed in the Colorado movie theater at age 24 shortly after moving to the state from San Antonio.

Phillips, who was in Washington on Wednesday, called the votes “very disappointing,” but she praised Landrieu.

“Sen. Landrieu had the courage and fortitude to stand up to the other senators,” Phillips said, adding that she will not forget the opposing votes. “We’re not giving up, and we’ll be back to fight another day.”