Knowing that television cameras would beam images of the hearing nationally, both sides were drumming up supporters to attend Wednesday's session.
A page on an NRA-related website urged backers to arrive two hours early to get seats, bring no signs and dress appropriately. The liberal BoldProgressives.org urged its members to attend, saying the NRA "will try to pack the room with their supporters to deceive Congress into believing they are mainstream."
Earlier this month, President Barack Obama proposed a package that includes banning assault weapons, requiring background checks on all firearms purchases and limiting ammunition magazines to 10 rounds.
Giffords underwent a lengthy rehabilitation process and has regained some ability to speak, but has retired from Congress. A gun owner, she and her husband Mark Kelly, a retired astronaut, have formed a political action committee called Americans for Responsible Solutions to back lawmakers who support tighter gun restrictions.
In testimony prepared for the hearing but released Tuesday, Wayne LaPierre, NRA executive vice president, said such steps had failed in the past. He instead voiced support for better enforcement of existing laws, beefing up school security and strengthening the government's ability to keep guns from mentally unstable people.
The massacre in Newtown has also set off a national discussion about mental health care, with everyone from law enforcement leaders to the gun industry urging policymakers to focus on the issue as a way to help prevent similar mass shootings. The issue of mental health has arisen in four recent mass shootings, including Sandy Hook, the Tucson shooting, the incident in an Aurora, Colo., movie theater last year and Virginia Tech in 2007.
"Law-abiding gun owners will not accept blame for the acts of violent or deranged criminals," LaPierre said in his statement. "Nor do we believe the government should dictate what we can lawfully own and use to protect our families."
While not yielding on specifics, much of LaPierre's statement had a milder tone than other remarks the NRA has made since Newtown.
That includes an NRA television ad calling Obama an "elitist hypocrite" for voicing doubts about having armed school guards while his own children are protected that way at their school. While Obama's children have Secret Service protection, officials at their school have said its own guards don't carry guns.
Feinstein said Tuesday that she will hold her own hearing on gun control because she was unhappy that three of the five witnesses testifying Wednesday are "skewed against us."
Senate Minority Leader Mitch McConnell, R-Ky., said Tuesday he would wait to see what legislation Democrats produce. Republican leaders of the GOP-run House have expressed similar sentiments.
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