Democrats are dropping another universal background-check bill. Here's what to expect this time.

House Democrats will introduce new legislation Tuesday meant to enact universal background checks, one of the biggest promises made by House Speaker Nancy Pelosi and other top Democrats ahead of the November midterms. But even as 2018 ended with at least 340 mass shootings and huge public support for universal background checks, the bill will still face a tough battle to become law.

Its major sponsors include Pelosi and Rep. Mike Thompson, another California Democrat, who chairs the Gun Violence Prevention Task Force, plus GOP Rep. Peter T. King, serving as a co-sponsor; more Republicans are expected to sign on. Former Rep. Gabrielle Giffords of Arizona, who survived a mass shooting that targeted her at a 2011 constituent meeting, will join the co-sponsors for the bill’s introduction in Washington.

In the Senate, Democratic Connecticut Sens. Chris Murphy and Richard Blumenthal will introduce similar legislation this week. But the wider Senate, still controlled by the GOP, likely won’t take it further.

When it comes to gun control, universal background checks are about as bipartisan an option as they come, but Republicans fearing NRA retribution have typically blocked legislative efforts. Back in 2017, Thompson and King introduced similar legislation for background checks — that ultimately went nowhere under a GOP-controlled Congress — and they managed to attract 14 GOP co-sponsors. The new legislation will not address more progressive gun-control actions, such as an assault weapons ban, and will include notable exceptions such as exchanges between family members.

But what exactly will universal background checks change? And does this bill have any real chance of passing? Here’s what you need to know.

Right now, licensed firearms dealers are required to run a buyer’s name through a federal database that will flag any potential issues from the purchaser’s past. The laws can get more stringent, depending on the state. At the federal level, there are numerous disqualifiers for potential gun buyers:

• Fugitives
• People deemed mentally unwell by the state
• Domestic abusers
• People who renounce U.S. citizenship
• Convicted felons
• Convicted drug users
• Non-citizens
• Dishonorably discharged veterans
• Most people with restraining orders

Since they became law in 1994, federal background checks have prevented gun sales to some 3 million people, according to the Department of Justice.

In the United States, background checks are required for anyone buying a firearm from a federally licensed dealer. The problem is the large loophole for “private sales,” such as those that happen at gun shows (there are hundreds every year) or in exchanges between friends and family members.

As much as 40 percent of gun sales in the U.S. occur without a background check. Universal background checks seek to close these loopholes by requiring background checks for all sales, even those that don’t involved federally licensed dealers.

The bill will pass the House, which is now handily controlled by the Democrats. Otherwise, its fate is uncertain. Republicans, who received hundreds of thousands of dollars in 2018 from the National Rifle Association, control the Senate. Even if the bill does make it to President Donald Trump’s desk, its future seems bleak. The president once seemed open to the idea of universal background checks, though he later walked this back, so it’s possible that he could veto the bill even if it manages to make it through the Senate.

“It is going to be difficult. We will likely have to find about a dozen Republicans who will vote with us, but there are lots of Republicans who are on the ballot in 2020,” Murphy said at a press conference announcing the Senate measure Monday. He said the House will be a litmus test for how much bipartisan support the measure has.

In 2017, more than 200 members of the House co-sponsored a bill for universal background checks but just 14 of them were Republicans. The most successful attempt Congress has made toward implementing universal background checks happened in 2013 shortly after the shooting at Sandy Hook Elementary School, where 20 children and six educators were gunned down. The bill, though supported by 90 percent of Americans, failed to gather enough Republican support to avoid a filibuster.

Recent national polls have tallied general support for universal background checks as high as 97 percent. Nevertheless, the NRA still opposes expanding background checks.

Cover: In this May 4, 2018, file photo, attendees walk by a display of AR-15s and AR-10s at the National Rifle Association convention in Dallas. (AP Photo/Sue Ogrocki, File)