SALEM -- A bill to require criminal background checks for private gun transfers cleared its biggest hurdle Tuesday when it passed the Senate on a 17-13 vote.

House Democratic leaders now appear set to quickly move the measure through their chamber, which would end a long legislative fight over the issue sparked by the 2012 mass shootings at an elementary school in Newtown, Connecticut, and at Clackamas Town Center in the Portland suburbs.

"It's a common-sense proposal providing common-sense safeguards," said House Majority Leader Val Hoyle, D-Eugene, who added that the first House hearing could come as early as next week.

Senate passage of the bill was preordained when Democrats won two additional Senate seats in the elections last year, giving them the votes to move a measure that stalled in the last two sessions.

Everytown for Gun Safety, which billionaire Michael Bloomberg said he planned to fund with $50 million, helped win those two Democratic seats. This year, the group has been lobbying and advertising in favor of the Oregon measure.

Tuesday's nearly two-hour debate over Senate Bill 941 on the Senate floor was an intense and emotional encapsulation of the long national argument over regulation of firearms.

Republicans, who unanimously voted against the bill, argued that it would unfairly burden law-abiding gun owners while doing nothing to stop criminals.

"We all know that criminals are not going to abide by this law," said Sen. Tim Knopp, R-Bend. "They do not buy guns from people who can identify them later. They steal them."

Among Democrats, only Sen. Betsy Johnson of Scappoose voted against the measure.

Sen. Floyd Prozanski, D-Eugene, the chief sponsor, said the bill closes a major loophole. Under current Oregon law, background checks are required on people who buy firearms from a gun dealer or at a gun show to ensure they aren't a felon or aren't otherwise prohibited from owning a firearm -- but not when individuals privately sell or trade guns.

"Why would I vote no on a bill that would make it harder for the guy who murdered my sister to obtain guns?," said Prozanski, whose sibling was shot to death in 1973.

Prozanski's measure includes a provision that he argued could play an important role in reducing gun violence. It would require judges who order someone to receive outpatient mental care to determine whether that person should also be barred from gun ownership while they are in treatment. Under current law, generally only those who are involuntarily committed for treatment lose their gun rights.

Supporters of the bill argued that the rise of the Internet has made it easier for people to buy and sell guns without background checks.

It's illegal to sell guns across state lines without working with a licensed dealer who requires a background check. But individuals in the same state can agree to meet somewhere and complete a firearms transaction without outside scrutiny.

Everytown for Gun Safety said it found that as many as 25,000 guns a year are being offered for sale in Oregon through four websites specializing in firearms sales.

Gun-rights supporters question whether that many sales occur and say gun owners often make sure to conduct a background check if they're selling to someone who seems suspicious.

Many gun owners who like to buy and sell guns say the background checks amount to a stiff tax on their hobby. Oregon State Police charge $10 for a background check, and SB 941 would require that any such checks go through a licensed dealer, who can also add to the charge.

Sen. Kim Thatcher, R-Keizer, said SB 941 would create a long list of "untenables" confronting average gun owners. For example, she said, a gun owner worried about the stability of someone in his or her home wouldn't be able to temporarily store guns with a friend without going through a background check. An unmarried couple living together would need a background check to swap a gun, she said.

Prozanski countered that he doubts officials would pursue anyone in such circumstances. He noted that his measure has exemptions, including for family members and people who lend guns for hunting.

Senate Minority Leader Ted Ferrioli, R-John Day, charged that the measure in essence would lead to gun registration because authorities could find out about all firearms transfers.

"This is the path to Ruby Ridge for Oregon," said Ferrioli, referring to the bloody Idaho siege in 1992 between federal agents and survivalist Randy Weaver and his family. Just as in Idaho, he said, it could lead authorities into trying to confiscate guns from people they don't think should have them.

Hoyle, the House majority leader, said she is confident the bill has the votes to pass in her chamber, where Democrats hold a 35-25 majority. In the unlikely event it doesn't, she said, she is confident Everytown and other groups would take the issue to the ballot.

"That's always been an option," said Jake Weigler, a political consultant working with the Oregon Alliance for Gun Safety. "We know these measures have always been supported by the public and it passed in Washington [state] last year."

-- Jeff Mapes

503-221-8209

@Jeffmapes