BART's decision to start enforcing a little-known safety measure and roust people sleeping or lying in its downtown San Francisco stations is aimed at ending the deadlock over what to do about the underground system becoming a de facto homeless shelter.

"For years the city would do sweeps, and the result was that the homeless would just go down into the stations," said one transit agency official, who asked not to be named because of the political sensitivity of the crackdown.

And while San Francisco was enacting laws against sitting or lying to block a sidewalk, BART held off - in part because even the elected BART directors were split on what to do, with some reluctant to be seen as kicking homeless people out into the cold.

Meanwhile, station agents who feared for their well-being were asking for police protection.

Then, about six months ago, a BART police sergeant came across a little-known state safety code that bars people from blocking the exits of a transit station.

People lying down near an exit could endanger BART patrons' safety, police concluded.

When they met with city officials, they backed up their safety concerns with a video of an evacuation after an electrical arc filled the Civic Center Station with smoke back in 2012.

With that, the sleeping or lying went from being a homeless issue to a safety issue.

"I'm sure there are some directors who have concerns about it, but we are trying to do what is right," said BART board President Joel Keller.

In the air: The man accused of playing airport security agent and directing two women into a private screening area for pat-downs at SFO is not only a high-powered international financier - he's the son-in-law of the man who led Hong Kong's government when it was turned over to Chinese rule.

Tung Chee-hwa was Hong Kong's chief executive from 1997 to 2005. He told the South China Morning Post that he was aghast at the news that his son-in-law, 53-year-old Eric Slighton, was arrested on suspicion of public drunkenness after allegedly masquerading as a security screener at San Francisco International Airport on July 15.

"I see Eric as a good husband to my daughter and a responsible father to my grandchildren," Tung told the Hong Kong newspaper. "For now, I just hope we could give Eric and his family members some personal space and time to deal with these difficult moments."

Slighton has taken a voluntary leave of absence from his job as a director at Aktis Capital Singapore to deal with his legal problems, the newspaper said.

Slighton, who has addresses in San Francisco and Hong Kong, allegedly mingled with SFO's security screeners for some 40 minutes before he ushered the women into the pat-down area. He is due to appear in San Mateo County Superior Court on Aug. 18.

In the meantime, sheriff's investigators are still trying to track down the two women to determine if more serious charges are warranted.

Cha-ching! You'd think most of the Democratic donors attending Wednesday's breakfast roundtable with President Obama at San Francisco's Four Seasons Hotel and a luncheon at the Los Altos Hills home of developer George Marcus would be tapped out by now, given all the money the president has raised here already.

Not so, says one fundraising insider, who tells us the Dems have the U.S. Supreme Court to thank for allowing donors to give to an unlimited number of candidates and causes in any election cycle without worrying about bumping up against a total spending cap.

Democratic Party officials hope to pull in up to $1 million Wednesday, with much of the money going to the party's congressional campaign committee.

"It's Nancy's usual suspects" on the invite list, said our insider, referring to House Minority Leader Nancy Pelosi, D-San Francisco. "And that makes it easier."

Niners gala: The 49ers' traditional red and gold colors gave way to black tie Saturday night, with a gala at the new Levi's Stadium that featured John Legend performing on the 50-yard line.

The thousands of invited revelers were wined and dined with a menu that featured everything from sushi to sliders.

And no windy speeches.

Estimated cost to the team: $375 per person.

"It was spectacular," Santa Clara County Assessor Larry Stone said Tuesday as he wrote out a $310 check to cover the gift limit amount he exceeded by bringing his wife.

San Francisco Chronicle columnists Phillip Matier and Andrew Ross appear Sundays, Mondays and Wednesdays. Matier can be seen on the KPIX-TV morning and evening news. He can also be heard on KCBS radio Monday through Friday at 7:50 a.m. and 5:50 p.m. Got a tip? Call (415) 777-8815, or e-mail matierandross@sfchronicle.com.