WASHINGTON (CBSDC/AP) — Sen. Joe Manchin revealed that Newtown families told him that the gun background check measure that he co-sponsored with Sen. Pat Toomey would not have prevented the shooting at Sandy Hook Elementary School.

“First of all, they’ll come in and say we don’t want anybody’s guns to be taken away. We don’t want any infringements of the Second Amendment to be infringed upon,” Manchin said on CBS News’ “Face the Nation” on Sunday. “When they come to you and they’re saying, honestly, we know the bill you’re working on right now would not have prevented what happened to our babies. But if you can prevent one family from not going what we went through, by keeping the guns out of a mentally deranged person, out of a criminal that could do something … and the common sense to do the right thing, my goodness what a difference we could make.”

Adam Lanza, 20, killed 26 people, including 20 children, last December at Sandy Hook Elementary School.

Manchin appeared with Toomey Sunday on “Face the Nation” to push the background check measure they put together last week.

“[O]urs I think just strikes the right balance, extending background checks at gun shows we think makes a lot of sense, strengthening the existing background check system makes a lot of sense,” Toomey said.

The Toomey-Manchin amendment would expand background checks to cover transactions at gun shows and the Internet. The system, aimed at stopping criminals and others from getting firearms, now covers only sales handled by licensed gun dealers.

The fate of the measure remains uncertain, though, as seven Republicans amenable to a gun control debate are still likely to resist such an expansion.

In an initial showdown over the gun control bill last week, 16 Republicans voted to reject a conservative effort to derail the measure, a roll call that allowed debate on the legislation to begin. Gun control supporters are hoping they can get enough votes from this group to help win approval for expanded background checks, the cornerstone of the effort by President Barack Obama and others to reduce firearms violence.

So far, seven of the 16 have said they will oppose the bipartisan background check proposal, or are leaning toward doing so. Four said they will support it or are likely to, and the remaining members of that group haven’t indicated a position.

Two Democrats, both facing re-election next year in GOP-leaning states, voted against beginning the gun control debate last week.

There are 53 Democrats and two-Democratic-leaning independents in the Senate. Gun control advocates will need 60 votes for the background check proposal to survive.

The Senate will begin debate on the measure Tuesday and the vote will most likely occur Wednesday.

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