Joe Manchin and Pat Toomey will hold a press conference Wednesday. | AP Photos Deal unveiled for background checks

Sens. Joe Manchin and Pat Toomey unveiled a bipartisan deal to expand background checks for commercial gun purchases — including those at gun shows and online — Wednesday morning, opening a pathway for the biggest change in U.S. gun laws in nearly two decades.

The two lawmakers said the tragic shooting at the Sandy Hook Elementary School in Newtown, Conn., in mid-December, which left 20 young children dead, had changed the debate around guns and gun ownership, and convinced them some new gun control measures were warranted.


“I have to tell you candidly that I don’t consider criminal background checks to be gun control,” said Toomey, who has a lifetime “A” rating from the powerful National Rifle Association. “I think it’s just common sense.”

( PHOTOS: Politicians speak out on gun control)

Toomey said he and Sen. Mark Kirk (R-Ill.) will back the measure, but he would not predict whether other Republicans would back it as well.

“Nobody here in this great Capitol of ours with a good conscience could sit by and not try to prevent a day like that from happening again,” said Manchin of the Newtown shooting. “I think that’s what we’re doing.”

The bipartisan agreement could give political cover for enough Republicans to vote Thursday and exceed the 60-vote requirement needed to allow the Senate to proceed to what would be an emotional floor debate on gun control legislation. That debate could last one to two weeks before a final vote, said Senate aides.

The Manchin-Toomey proposal would require background checks for sales at gun shows and online, but it will exempt personal transfers from such checks.

It also calls for the creation of a “commission on mass violence” that will study the sources of, and ways to prevent, the mass shootings that have plagued the country over the last decade.

The NRA, which has dominated any gun-related bills moving through Congress for years, has already come out in opposition to the proposal.

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“Expanding background checks at gun shows will not prevent the next shooting, will not solve violent crime and will not keep our kids safe in schools,” the National Rifle Association said in a statement issued even before Manchin and Toomey finished their press conference.

“While the overwhelming rejection of President Obama and Mayor Bloomberg’s ‘universal’ background check agenda is a positive development, we have a broken mental health system that is not going to be fixed with more background checks at gun shows. The sad truth is that no background check would have prevented the tragedy in Newtown, Aurora or Tucson.”

Sen. Chuck Schumer (D-N.Y.), who has been closely involved in the gun talks, called Mark Kelly, husband of former Rep. Gabrielle Giffords (D-Ariz.), on Wednesday morning to inform them he had signed off on the agreement, according to a Senate aide.

Giffords was seriously wounded in a Jan. 2011 shooting that left six other people dead. Giffords resigned from Congress the next year, and she and Kelly — a former astronaut — have becoming leading gun-control advocates.

Schumer also spoke to Vice President Joe Biden and New York City Mayor Mike Bloomberg to give them details of agreement and his support for it.

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Schumer negotiated several changes to the initial Manchin-Toomey proposal, including striking language from the agreement allowing concealed permit holders to carry their weapons in other states, and limiting Internet sales to five guns per year. He also worked to make sure there is a 72-hour window for performing background checks except for gun-show sales, which will be cleared in 48 hours initially.

Kirk and Schumer were no-shows at Wednesday’s presser. Senate sources say Schumer in particular was directed to stay away at Toomey’s request.

The Manchin-Toomey agreement would close the so-called “gun show loophole” by requiring that background checks are conducted on all commercial gun sales in the country.

When a sale occurs, the buyer and seller would meet at a federally licensed dealer, who would conduct the check.

The dealer — not the government — would keep control of the sales record, as has been the process for the last four decades.

It would be a felony to sell a gun without a background check to a prohibited buyer or police officer.

Proponents of the Manchin-Toomey agreement, including the leading gun-control groups, say dealer records would help law enforcement trace guns recovered at crime scenes. However, person-to-person sales — the “friends and neighbors exceptions” would not be subject to a background check.

Senate Majority Leader Harry Reid (D-Nev.) moved Tuesday night to start debate over a legislation that is a wish list for gun control advocates, filing a cloture motion setting up a Thursday vote to end a GOP filibuster of the motion to proceed to that gun bill.

Even before Wednesday’s announcement by Manchin and Toomey - who have been trading proposals back & forth for the last week, Democrats believed they had could get enough GOP support to overcome a Republican filibuster led by Sens. Rand Paul (Ky.), Ted Cruz (Texas), and Marco Rubio (Fla.). Senate Minority Leader Mitch McConnell (R-Ky.) also said he would oppose the motion to begin debate on the gun bill.

The deal between Manchin, a West Virginia Democrat, and Toomey, a Pennsylvania Republican and the former head of the conservative Club for Growth, would be offered as an amendment to an existing Democratic gun bill.

In order to gather 60 votes, Reid and other senior Democrats believe they can hold on to their own nervous members from red states, while picking up 10 or so Republicans.

The bigger problem for Reid then becomes what can actually pass the Senate. Beginning debate is far from passing a bill, and without the political cover from the Manchin-Toomey agreement, there is no guarantee that Reid could get the 60 votes he would need for a final vote on any legislation.

“We’re going to vote Thursday,” Reid confirmed on Tuesday afternoon. “I’m going to file cloture on the bill tonight. It would be a real slap in the face to the American people not to do something on background checks, on school safety, on illegal trafficking, which everybody thinks is a good idea.”

When pressed by reporters, Reid conceded that he’s going to lose some Democrats on the cloture vote. And the majority leader said he hasn’t been pressing Democrats to support a measure that is political dynamite for those in red states, many of whom are up for reelection in 2014.

Reid said that if the bill doesn’t get 60 votes to move to the floor, he would then move to hold votes on individual bills for several gun proposals, including the assault weapons ban, background checks and limits on high-capacity magazines.

Toomey represents Democrats’ last hope of reaching a compromise gun deal including background checks with record-keeping of most gun sales, a provision that gun groups and many conservatives fiercely oppose but that has broad public support. Democrats hoped that if they lured one conservative ally, then others — along with gun-friendly Democrats — would follow.