DENVER -- Lawmakers moved closer on Friday to passing a package of new gun restrictions in Colorado, a state that has lived under the shadow of two of the worst mass shootings in United States history.
After hours of debate that lasted well into the evening, Colorado's House of Representatives gave initial approval to legislation requiring background checks on private gun sales and placing limits on ammunition magazines -- measures that were being watched nationally by advocates on both sides of the issue.
The bills were part of an array of gun proposals being pushed hard by state Democrats this year after the shooting at an Aurora movie theater last summer and the killings at an elementary school in Connecticut in December.
"There is a common thread that we see in these massacres," said State Representative Rhonda Fields, a Democrat from Aurora who sponsored both pieces of legislation and whose son was shot to death in 2005. "They're using high-capacity magazines so they can unleash as many bullets as they can, to kill as many people as they can, in our schools, our theaters and our churches."
The debate over whether to enhance restrictions on firearms has become a contentious focal point of state legislative sessions around the country this year.
Perhaps nowhere has this been the case more than in Colorado, a state with deep conservative and independent streaks. But it is also a place that has been pondering tougher guns laws since the Columbine school shooting in 1999, and the increasing influence of Democratic lawmakers in recent years has made gun-control legislation a political possibility.
Friday's debate on the House floor capped a week in which gun bills proposed by Democrats cleared several legislative committees, often after lengthy and emotional comments, mostly from proponents of gun rights. Republican legislators argued for hours against the measures, saying the proposed magazine limits -- 15 rounds for guns and 8 for shotguns -- were merely arbitrary and would have little effect on gun violence.
"It makes no difference to public safety if there are 10 rounds in a magazine, whether there are 15 rounds in a magazine or whether there are 30 rounds," said State Representative Jared Wright, a Republican from Fruita.
Republicans also sharply criticized the background check proposal. Sales of antique guns and gifts of guns between immediate family members would be exempt under the measure.
Those buying guns from federally licensed gun dealers must already undergo a background check in Colorado, as they do in every other state under federal law.
"All this bill does is make us law-abiding citizens go through another hoop," said State Representative Jerry Sonnenberg, a Republican from Sterling. "It doesn't stop criminals, those that can't get background checks, those that are felons, from breaking into my house and stealing my guns. Doesn't stop them from meeting a guy down the street and buying a gun there."
But with Democrats holding a majority in the House, both bills received preliminary approval. The bills must receive a final House vote, which could come as early as Monday, before heading to the State Senate, where Democrats also outnumber Republicans.
"We continue to hear that responsible gun owners do not commit crimes," said State Representative Beth McCann, a Democrat from Denver who sponsored the background check legislation with Ms. Fields. "So it's hard for me to understand how responsible gun owners would have any objections to this bill. All this is doing is requiring everyone to go through the same background check."
According to the Brady Campaign to Prevent Gun Violence, Colorado would join California, New York and Rhode Island as states that require sweeping background checks on virtually all gun purchases.
Currently, only four states prohibit magazines that hold over 10 rounds, while New Jersey bans magazines with more than 15 rounds and Maryland those with more than 20, the group said.
Two other gun measures put forth by Colorado Democrats also received preliminary approval on Friday by House lawmakers. One bill would ban concealed weapons on college campuses. The other would charge gun buyers for background checks.
Correction: February 16, 2013, Saturday
This article has been revised to reflect the following correction: An earlier picture caption incorrectly stated the city affiliation of State Representative Rhonda Fields, who sponsored the legislation. She represents Aurora, not Denver.
This article originally appeared in The New York Times.