A move to require background checks for nearly all gun transactions attracted a big crowd and strong emotions at the Legislature on Thursday.

“This is the public safety issue of the legislative session,” said Dennis Flaherty, representing state police officers and speaking in favor of the proposal.

“A lot of folks just don’t want their firearms tracked, taxed or taken,” said Chris Rager of the National Rifle Association, leading the charge against the bill.

Unlike the House, Senate leaders on Thursday immediately declared that a ban on assault-style weapons and other gun restrictions would not be under consideration, directing their efforts instead to a proposal for universal background checks, which rapidly is becoming the main battleground for this year’s gun debate. The bill would require background checks of virtually all sales of handguns and semiautomatic rifles, including those sold privately, at gun shows or through the Internet.

The debate, part of the national fallout over the massacre of grade-schoolers at Sandy Hook Elementary School in Connecticut in December, has filled committee rooms in St. Paul. It also has sparked a flurry of gun owners who want to carry their loaded weapons into the Capitol itself.

Licensed permit-holders may carry their weapons into the Capitol so long as they notify the Department of Public Safety. When the legislative session opened in January, there were 523 such notifications. As of Thursday, that number had spiked to 723 — an increase of 38 percent in six weeks. By comparison, in 2012 there were only 56 new gun-carrying notifications during the entire year.

On Thursday, as was the case when the House held similar hearings earlier this month, those wearing NRA and Second Amendment buttons outnumbered those on the gun-control and law-enforcement side.

Both sides were equally passionate.

Sen. Bobby Joe Champion, DFL-Minneapolis, said his bill aims to fill a gap in the current background check system — those person-to-person sales that are not now subject to such checks. Champion pointed out that his father is a hunter and that his bill is not aimed at the masses of law-abiding gun owners. He said transactions between family members would not be covered.

Closing the door

Flaherty, representing the Minnesota Police and Peace Officers Association, said national estimates show that 40 percent of all gun sales happen outside the federal or state background-check system. He said the number in Minnesota might be higher.

“We are not doing enough to protect the citizens of our state from gun violence,” said Flaherty. “This bill closes the door to people who should not have a handgun.”

Minneapolis Mayor R.T. Rybak, also arguing for the expanded checks, said the current system is akin to boarding a flight in which 40 percent of the passengers are not required to go through security. “Wouldn’t that make you less likely to fly?” he said.

Two people touched by gun violence — Samuel Rahamim, whose father died in the Accent Sign­age shootings in Minneapolis last September, and Mary Streufert, whose daughter was killed in 1991 — urged the committee to take action.

“Minnesota gun victims deserve a vote on these bills,” Streufert said.

The NRA’s Rager questioned the 40 percent number, saying the actual number of nonchecked sales is much smaller. He accused Champion of essentially “banning private sales” by requiring that the two parties go through a licensed gun dealer and pay a fee for the background checks. He said it already is illegal for someone to sell weapons for profit without a license, adding, “There is no gun-show loophole.”

One new wrinkle in the debate is that some gun-rights supporters find themselves on the same side as mental-health advocates. The bill contains language that would allow officers to deny permits to a larger number of people who have struggled with mental illness — not just those who have been committed in a court proceeding.

Would veterans be affected?

Rager said he is concerned about disqualifying a greater number of those with mental illness and suggested it could affect veterans of the wars in Iraq and Afghanistan who are suffering from post-traumatic stress disorder.

Michael Undlin of Plymouth, testifying against the bill, said he struggled with anxiety and depression but has no violent tendencies. Under the bill, he said, “If I keep my gun, I’m a criminal.”

Kevin Vick, a licensed firearms dealer from Lakeville, also opposed the bill. He said he supports a federal background-check system, even though he admitted it needs to be improved. He said that Champion’s bill would not have prevented many recent mass killings and that it would not stop street criminals from finding weapons.

“Criminals have not and will not subject themselves to universal background checks,” he said. He urged the committee not to approve “feel-good, knee-jerk, politically expedient bills.”

A second bill to come before the committee attracted little debate. Supported by Hennepin County Attorney Mike Freeman, it would tighten state law to ensure that certain violent offenders and juveniles would face stiff penalties for illegally possessing guns.