The Senate is still under Republican control, which means the likelihood that such a bill would make it to President Donald Trump’s desk is slim. Senate Majority Leader Mitch McConnell has signaled that he wouldn’t take up a bill like this, and it’s unclear if Trump would sign it even if he did. Still, Democrats and gun-control advocates view the potential move as an important symbol.

Since 1994, a federal background check has been required for every individual purchasing a firearm from a federally licensed gun dealer. But experts estimate that some 20 percent of gun sales occur over the internet or at gun shows, from unlicensed dealers. Thompson’s bill would change that. The legislation, which will likely be co-authored by Republican Representative Peter King of New York as well as several other as yet unnamed lawmakers, would require federal background checks on virtually all types of gun sales, with just a few exceptions.

Read: As students ‘march for our lives,’ what are the feasible aims for gun control?

A majority of both gun owners and non–gun owners support universal background checks, according to the Pew Research Center, and researchers argue that expanding them works: States that already require background checks on all gun purchases experienced 35 percent less gun deaths per capita than states without the requirement, according to the Centers for Disease Control and Prevention.

Thompson and King proposed similar legislation last year, but their bill was never taken up by Republican leadership for a vote. Now, though, things have changed. Democrats won back a decisive majority in the House in November, and activists claim that the tide is shifting.

“The passage of a universal-background-check bill is something that we haven’t seen in 20 years,” said John Feinblatt, the president of Everytown for Gun Safety, “probably the most convincing proof yet that American political leaders are catching up with the American people.”

In the 10 months since 17 students and staff members were killed in the mass shooting at Marjory Stoneman Douglas High School in Parkland, energy has amassed on the side of grassroots gun-control groups and prompted nationwide marches and student walkouts. In the 2018 midterms, these groups outspent the National Rifle Association for the first time in history, according to the Center for Responsive Politics. Revenue at the NRA reportedly declined by 15 percent in 2017, and its membership dues dropped to a five-year low. On Tuesday, the Trump administration unveiled a new regulation officially banning bump-fire stocks.

“The pattern has been pretty predictable, where for too long a tragic shooting occurs, it captures the attention of the nation, the country mourns, political leaders ask for prayers, and then the gun lobby ends up getting its way,” Feinblatt said. “There’s no question [people] are convinced it’s time to break the pattern.”