New York City Mayor Michael Bloomberg and Boston Mayor Thomas Menino, the co-chairmen of Mayors Against Illegal Guns, echoed that support, arguing that the Senate measure is a "commonsense" approach to keeping guns out of the hands of those who would use them on others.
Unveiled Wednesday by Sens. Joe Manchin (D-W.Va.) and Pat Toomey (R-Pa.), the new proposal would require private gun sellers operating at gun shows and online to conduct background checks on all potential buyers. That mandate is an expansion of current law, which requires such screenings only of federally licensed gun dealers.
The bill is opposed by the National Rifle Association (NRA) and conservative Republicans wary that the additional requirements will sap rights guaranteed by the Constitution.
"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 NRA said Wednesday in a brief statement.
But Toomey on Wednesday rejected those attacks outright.
"I don't consider criminal background checks to be gun control; I think it's just common sense," Toomey said Wednesday at a press briefing in the Capitol. "The worries that we hear sometimes about background checks leading to an erosion of our Second Amendment rights, it simply hasn't happened."
The bipartisan agreement on one of the central elements of President Obama's strategy to tackle gun violence lends the agenda a great deal of momentum as it heads to the Senate floor later this week. Although a number of Senate Republicans, including Minority Leader Mitch McConnell (Ky.), have vowed to filibuster the package, it appears they lack the 40 votes needed to block it.
The Senate package also includes tougher penalties for gun trafficking and efforts to enhance security at the nation's schools. It comes in direct response to December's shooting massacre in Newtown, Conn., where a gunman stormed into an elementary school and killed 20 children and six adults with a military-style rifle.
McCarthy said she still has "high hopes" that even tougher reforms, like a ban on high-capacity ammunition magazines, can find legs in Congress despite the odds against them. But she was quick to add that she won't oppose anything she considers progress in the battle against gun violence.
"I'm thrilled that we're going forward," she said.
It remains unclear what House GOP leaders intend to do if the Senate sends over a gun control package. Speaker John Boehner (R-Ohio) sidestepped the question Wednesday, saying only that he wants to see what the Senate can pass.
McCarthy, for her part, predicted Boehner will have to deal with the issue soon enough.
"When he says nothing, I don't know what he means by that," she said. "The Senate will pass legislation."