Washington – More than six years after the Newtown shootings, the U.S. House of Representatives plans this week to pass a bill introduced in response to that massacre that would mandate federal background checks on all gun sales, including private transactions.

The expanded background check bill has faltered several times in the Senate, and was never considered before on the House floor.

But the GOP’s loss to the Democratic Party last November, and the influx of new gun control supporters — especially among the freshman class — has changed the political landscape in the U.S. House.

Everytown for Gun Safety — financed by billionaire businessman and former New York Mayor Michael Bloomberg — poured millions of dollars into the 2018 House races in support of pro-gun control candidates, ensuring quick action on the issue this year.

“Elections matter folks,” tweeted Sen. Chris Murphy, D-Conn., in response to an announcement by the bill’s sponsor, Rep. Mike Thompson, D-Calif., that the bill would finally get a vote in the U.S. House.

Murphy was a lead sponsor of the bill in the Senate, conducting a 15-hour filibuster in 2016 to pressure GOP leaders to allow a vote on the bill. They did, and it failed to garner the 60 votes needed to advance in that chamber.

The expanded background check bill would require FBI background checks of prospective buyers for individual gun sales on the Internet and at gun shows.

Right now, if a background check is not completed in three days, the weapon is sold anyway.

The bill would extend that three-day deadline to as many as 20 business days to close the “Charleston Loophole.” That loophole allowed white supremacist Dylann Roof, who killed nine African-Americans at the Emanuel AME Church in Charleston, S.C., in 2015, to buy a gun despite pending felony drug charges against him.

While the legislation is expected to pas the House, it may stumble in the Senate, which is still under Republican control. And there’s concern President Donald Trump would not sign it into law, even if it does pass both chambers.

“Speaking realistically, the immediate objective is to muster the most votes possible in the House to create momentum in the Senate,” said Sen. Richard Blumenthal, D-Conn.

He said a strong  House vote, likely held Wednesday or Thursday this week, will create a “tide” that would be “more difficult for [Senate Majority Leader] Mitch McConnell to resist.

The National Rifle Association opposes the bill, saying it would lead to a national gun registry.

The NRA also says the legislation would “make criminals out of law-abiding gun owners for simply loaning a firearm to a friend or some family members.”

Meanwhile, gun control groups are trying to exert pressure on lawmakers who have not cosponsored the background check bill.

“Find out which Members of Congress have NOT yet cosponsored the background check bill #HR8 that 97% of Americans support. Congress has NOT passed a single gun control bill in 25 yrs. Tell them to take action to #EndGunViolence or we will #VoteThemOut,” tweeted the Newtown Action Alliance.

The alliance was created shortly after the shooting of 20 first graders and six educators at Sandy Hook Elementary School in December of 2012.

Since that shooting, Connecticut has toughened its gun ownership regulations.

Under state law, handgun transfers cannot be made until the person making the transfer obtains an authorization number – following a background check on the prospective purchaser – from the Connecticut Department of Emergency Services and Public Protection.

The state also requires all gun owners to have a permit.

But gun control advocates in the state say tougher federal regulations are needed, too, to make it more difficult for guns purchased outside the state under laxer laws to come into Connecticut.