WASHINGTON - Sen. Dianne Feinstein's long pursuit of stricter gun laws began more than three decades ago on a day of bullets and bloodshed in San Francisco.

On Nov. 27, 1978, former supervisor Dan White walked into City Hall with a grudge and a .38 revolver.

He fatally shot Mayor George Moscone, walked past Feinstein's office and then turned his weapon on Supervisor Harvey Milk, one of the country's first openly gay elected officials and a rising political star.

A stunned Feinstein, who at 45 was president of the city's Board of Supervisors, had lost two bids for mayor and wasn't planning to run for re-election. Then she announced the deaths of her colleagues to a city in a state of shock that looked to her to lead.

The shootings recast her political career, becoming its consequential moment and one that has forever defined her in the public sphere. It also infused Feinstein with an unwavering advocacy for an issue that comes when you've reached into the bloody wound of a colleague and frantically - but fruitlessly - searched for a pulse.

As senator, she led the campaign to pass the original federal assault weapons ban in 1994, but it expired in 2004, and she couldn't attract enough support for renewal. The massacre of 20 elementary school children and six adults in Newtown, Conn., in December, so shocked and reviled the nation that she is trying again.

But nearly three months after the massacre, every co-sponsor of Feinstein's bill, the Assault Weapons Ban of 2013, is a Democrat. Not a single Republican has added a signature.

"I thank those who are with me," Feinstein said last week as the Senate Judiciary Committee began voting on amendments to the bill. "I don't know that I can convince those who are not, but I'm going to keep trying."

Her legislation would ban assault weapons nationally, restrict the sale of ammunition clips with more than 10 bullets and expand background checks to gun shows and private sales.

The 79-year-old Feinstein will likely not get all she wants. Her opponents, led by the National Rifle Association, which frustrated her efforts to renew the assault weapons ban in 2004, still wield considerable influence on Capitol Hill.

If it passes the committee this week, it would go before the full Senate for a vote. But passage is far from guaranteed.

Through two terms as mayor of San Francisco, an unsuccessful run for governor and more than two decades in the U.S. Senate, no issue has motivated Feinstein more than stopping gun violence, according to current and former colleagues and members of her staff.

When Feinstein became mayor, the .38 revolver that White used to kill Milk and Moscone was a standard-issue weapon in police departments. When she became a senator, police had increased their arsenal to match what they were up against on the street. But Feinstein said it's not enough.

"These weapons, which are really designed to kill as many people in close combat as big clips will allow, become attractive to grievance killers, gangs, and people who are not all there mentally," Feinstein said in an interview.

Her opponents, particularly NRA Executive Vice President Wayne LaPierre, have accused her of a "decades-old agenda" against guns. During a hearing last month on her bill, the NRA used Twitter to ridicule her knowledge of firearms and question the credibility of the law enforcement witnesses called to testify in support of its gun restrictions.

"In the hour that (she) has been holding her hearing aimed at banning AR-15s," read one tweet, referring to a type of weapon Feinstein would like to see off the streets, "Americans have bought 150 more." Then it urged opponents to stop her.

Feinstein has said that her repeated attempts to ban assault weapons are not intended to prevent people from defending themselves.

"She's not afraid of guns," said Susan Kennedy, a political consultant and former Feinstein aide.

After a militant anti-capitalist group called the New World Liberation Front unsuccessfully tried to bomb her house in the 1970s, Feinstein trained to use one.

"I know the urge to arm yourself, because that's what I did," she told Senate colleagues in 1995. "I made the determination that if somebody was going to try to take me out, I was going to take them with me."

To Feinstein, the battle is about keeping what she considers weapons of war out of the hands of those who intend to massacre innocent people. Her personal experience isn't all that impels her to wage it.

Before the December shootings at the Sandy Hook Elementary School in Newtown, there was the Cleveland Elementary School shooting in Stockton in January 1989. A 26-year-old man opened fire on a group of children with an AK-47, killing five and wounding more than 30 before taking his own life.

Before the movie theater shooting in Aurora, Colo., last July that resulted in 12 deaths and injuries to 58 others, there was the office tower shooting at 101 California Street in San Francisco in July 1993. A gunman with a grudge against a law firm shot and killed eight people before killing himself.

As time has passed, the tragedies have faded from public memory. But Feinstein has not forgotten.

"This is something I'm deeply passionate about, and I believe it saves lives," she said. "I don't intend to stop."

A veteran lawmakers who knows how to work behind the scenes and across the aisle, Feinstein ranks 14th in Senate seniority. Besides her seat on the Judiciary Committee, she serves on the powerful Appropriations Committee and chairs the Senate Intelligence Committee.

Her political roots took hold at a time before bitter partisanship began to color every debate, and even relationships on Capitol Hill.

One of her closest friends has been former Sen. Kay Bailey Hutchison, a Texas Republican who left the Senate in January. In an era fraught with political polarization, she has warm relations with many more lawmakers.

Sen. Jeff Sessions, R-Ala., a staunch conservative who serves alongside the liberal-leaning Feinstein on the Judiciary Committee, said that while they disagree on many issues, including the assault weapons ban, he admires her ability to forge compromise.

"I'd say on the 16 years I've been on it, she's been one of the more effective Democratic senators at reaching across the aisle on key issues," he said. "She battles for what she believes in, but she's also very able at finding common ground and solving problems."

In the latest fight over assault weapons, however, common ground appears to have eluded her. It will be a tough vote for some lawmakers, including several Democrats who face re-election next year.

Feinstein said there was "no magic formula" to collecting enough votes to pass her bill. But political handicappers give the assault weapons ban little chance in either chamber, and any restriction on the size of ammunition clips could also be a tough sell. Early signs point to a possible consensus on strengthening background checks.

Friends and colleagues said Feinstein will push as hard as she can for every measure she's proposed, but that ultimately she'll take something over nothing.

"At the end of the day, that's what every elected official has to do," said former California Gov. Gray Davis, whom Feinstein defeated in the 1992 Democratic Senate primary. "But she wouldn't take on this fight if she didn't think she could win."

Lawmakers were hardly unified on the idea of banning assault weapons 20 years ago when the first measure passed.

"Many people thought she was on a fool's errand," Davis said.

The NRA and other critics contend that the ban and other measures would do little to stop criminals from buying guns and instead punish law-abiding gun owners. But Feinstein said she said that if the original assault weapons ban had not expired, it might have continued to dry up the supply and maybe even have prevented Newtown and other tragedies.

"I've seen what's happening in our society as a product of these," she said. "It's just too much. We can put an end to it, and we should."

She said polls show that a majority of Americans support the assault weapons ban, and that many gun owners disagree with the NRA's position. Rather than forcing legislation the public doesn't want, she said she's responding to the public will.

But even with the Aurora and Newtown shootings still fresh in the nation's consciousness, "this is one of the biggest battles she will have in her career," Kennedy said.

Feinstein's efforts have the support of law enforcement agencies, medical associations, religious organizations and mayors across the country. New York City Mayor Michael Bloomberg, a leading gun control advocate, and former Arizona Rep. Gabrielle Giffords, the victim of a shooting rampage, and her husband, retired astronaut Mark Kelly, are among her allies. Both are longtime gun owners. President Barack Obama also supports her bill.

"The NRA is not going to slow her down," Davis said.

She's beaten the odds before. In April 1983, Feinstein faced a recall election in her first term as mayor, organized by a communist group that opposed a citywide handgun ban that she had signed.

The ban lost in court, but she won the recall with 81 percent of the vote.

"I don't think this will stop anyone from filing against me, but I think anyone who does is going to be creamed," Feinstein said at the time, daring anyone to challenge her in the November election. Again, she prevailed.

Call Curtis Tate, Bee Washington Bureau, (202) 383-6018.

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