Senators quickly splintered along partisan lines over gun control measures on Tuesday as Democrats demanded action in the wake of two mass shootings in the past week and Republicans denounced their calls, highlighting the political divide that has fueled a decades-long cycle of inaction on gun violence.
At a hearing of the Senate Judiciary Committee that was scheduled before shootings in Atlanta and Boulder that left at least 18 people dead, Democrats argued that the latest carnage left Congress no choice but to enact stricter policies. They lamented the grim pattern of anguish and outrage followed by partisanship and paralysis had become the norm following mass shootings.
“In addition to a moment of silence, I would like to ask for a moment of action,” said Senator Dick Durbin, Democrat of Illinois, and the chairman of the committee. “A moment of real caring. A moment when we don’t allow others to do what we need to do. Prayer leaders have their important place in this, but we are Senate leaders. What are we doing?”
Even before the recent shootings, Democrats had already begun advancing stricter gun control measures that face long odds in the 50-50 Senate. House Democrats passed two bills this month aimed at expanding and strengthening background checks for gun buyers, by applying them to all gun buyers and extending the time the F.B.I. has to vet those flagged by the national instant check system.
But the twin pieces of legislation passed in the House have been deemed too expansive by most Republicans — only eight House Republicans voted to advance the universal background check legislation. The bills would almost certainly not muster the 60 votes needed to clear a filibuster in the Senate.
Senator Chuck Grassley of Iowa, the top Republican on the panel, said in his opening remarks that he was hopeful Democrats and Republicans could work together to make “bipartisan, common-sense” progress on gun control. But he said that the House-passed legislation did not fit that bill, since the measures passed almost entirely along party lines.
“That is not a good sign that all voices and all perspectives are being considered,” Mr. Grassley said.
Senator Ted Cruz, Republican of Texas, went further, lashing out at Senator Richard Blumenthal, Democrat of Connecticut, who said that Republicans had offered “fig leaves” rather than actionable, significant solutions to gun control.
“Every time there’s a shooting, we play this ridiculous theater where this committee gets together and proposes a bunch of laws that would do nothing to stop these murders,” Mr. Cruz said. “But what they propose — not only does it not reduce crime, it makes it worse.”
The renewed focus on gun control is expected to cast attention back on Senator Joe Manchin III, Democrat of West Virginia, who opposes dismantling the legislative filibuster but has long labored — fruitlessly — to pass a bipartisan gun control proposal.
Following the 2012 shooting massacre at Sandy Hook Elementary School in Newtown, Conn., Mr. Manchin brokered a deal with Senator Pat Toomey, Republican of Pennsylvania, to close legal loopholes that allow people who purchase firearms at gun shows or on the internet to avoid background checks, but proponents were unable to pick up enough support to pass it.
Mr. Manchin told CQ Roll Call earlier this month that he opposed the House-passed universal background check bill, citing its provision requiring checks for sales between private citizens, but said he was interested in reviving the Manchin-Toomey legislation.