The gathering was emotional, as former Rep. Gabriel Giffords, D-Ariz., urged supporters of gun control legislation to "fight, fight, fight."

"Be bold. Be courageous. The nation is counting on you," Giffords said at a Capitol news conference.

Giffords, who was critically wounded when she was shot in the head in 2011 in a Tucson shopping center parking lot, is still physically disabled from her wounds.

Sen. Catherine Cortez Masto, D-Nev., thanked Giffords and recalled the horror of the 2017 Route 91 Harvest music festival mass shooting in Las Vegas that left 58 people dead and hundreds more wounded.

"My niece was at the concert, and my niece came home. But there were many families at the reunification center waiting to hear from their loved ones who never made it home," Cortez Masto said.

"Those are the people who we are fighting for, and they are not Republican or Democrat or independent. They're our neighbors. They're our friends. They are the ones who want us to do something about it," she said.

Nevada has passed a background check bill. Last week, Gov. Steve Sisolak, a Democrat, signed into law comprehensive gun control legislation during a ceremony in Las Vegas.

House bill languishing

"If we can do it in Nevada, we can do it across this country and we can do it in the United States Senate," Cortez Masto said.

The House passed a universal background check bill more than 100 days ago that closed loopholes that once exempted sales of weapons online and at gun shows.

It is the first gun control legislation passed in the House in a decade and comes after Democrats took control of the lower chamber this year.

Democrats and gun control advocates have called on Senate Majority Leader Mitch McConnell, R-Ky., to take up the legislation in the Senate.

McConnell has blocked bills passed by the Democrat-controlled House, criticizing Democratic leaders for passing what he says is messaging legislation that is out of step with voters.

"I am indeed the 'Grim Reaper’ when it comes to the socialist agenda that they have been ginning up over in the House with overwhelming Democratic support, and sending it over to America," McConnell said in an interview with Fox News.

Backers of the background check bill used that moniker against him during the news conference in front of the Capitol.

Sen. Richard Blumenthal, a Democrat from Connecticut, where 28 children died in the 2012 mass shooting at an elementary school, said McConnell would have "blood on his hands" if he did not allow the Senate to take up the House-passed bill.

Background checks popular

And an advocacy group headed by Giffords, using figures by the Centers for Disease Control and Prevention, calculated that 11,000 people have died because of gun violence since the House passed its bill - many due to domestic violence and shootings that claim an estimated 100 lives each day.

A poll by Quinnipiac University in February 2018 found that 97 percent of the survey’s respondents supported background checks, including 97 percent of current gun owners.

The shooter in the Sandy Hook Elementary School killings, Adam Lanza, used weapons purchased legally by his mother and stored in their Connecticut home.

And the Route 91 shooter, Stephen Paddock, also purchased his weapons legally and equipped more than a dozen assault rifles with bump stocks, which accelerate the rate of fire to nearly that of fully automatic weapons, before the 64-year-old opened fire on concertgoers gathered below his 32nd-floor Mandalay Bay hotel room.

A Trump administration ruling on bump stocks was implemented this year after the president ordered the Bureau of Alcohol, Tobacco, Firearms and Explosives to revisit rulings on the devices during the Obama administration.

But the lack of federal legislation to outlaw the devices has prompted more than a dozen states, including Nevada, to take state action against bump stocks.

Sisolak signed into law several bills last week that ban bump stocks, allow authorities to take guns from those who exhibit signs of doing harm to themselves and or others, and implement safe storage measures to limit access to weapons for children or those who could harm others.

Sisolak signed the bills in Las Vegas, a symbolic gesture for a city still traumatized by the Harvest festival tragedy that left an emotional strain on the city’s first responders and medical system.