Attorney general and gubernatorial candidate Doug Gansler listens to reporters after his remarks during a Thursday news conference in Silver Spring. (Bill O'Leary/The Washington Post)

A month after launching his campaign for governor, Maryland Attorney General Douglas F. Gansler was entangled Thursday in yet another controversy, this time acknowledging a lapse in judgment when he appeared at a beach-house party and did nothing to stop apparent underage drinking going on there.

At a half-hour news conference in Silver Spring, Gansler (D) said that when he stopped by a party for graduating high school students in June, he should have been more vigilant about ensuring that the teenagers were not doing anything illegal. A photograph shows Gansler in the middle of a party scene, surrounded by young people. He said that failing to more thoroughly investigate what was going on at the party was “a mistake I made.”

“In hindsight, I probably should have assumed there was drinking and talked to the chaperones about what they thought was appropriate,” Gansler said. But Maryland’s top law enforcement official said he was there as a parent, hoping to talk briefly to his teenage son about travel plans, and not as “a police officer or anything else.”

He saw teenagers drinking from red plastic cups that night, Gansler said. “There could be Kool-Aid in the red cups,” he said, “but there’s probably beer in the red cups.”

Gansler, 50, called the news conference in response to a Baltimore Sun story that included a photograph of him amid a throng of teenagers, three of whom were dancing on a tabletop.

At a news conference Thursday in Silver Spring, Maryland Attorney General Doug Gansler (D) said that he should have investigated whether there had been underage drinking at high school "beach party" where he stopped by to visit his son. (WJLA/NewsChannel 8)

At the news conference, Gansler was shown a copy of the photo that appears to show him holding a phone. When asked whether he was taking a photo with it, he said he had not yet learned how to do that with his new iPhone. He said he thought he was reading a text message.

Gansler told reporters that he visited “a dance party with loud music” to tell his son what time they had to leave Delaware in the morning. “What I’m doing in that picture is walking through — my son was upstairs; he was the DJ,” he said. “I walked through the party, walked through the dance floor, walked upstairs, talked to my son, walked downstairs and left.”

In the photograph, two other adults can be seen in the corner of the room, one of them holding what appears to be a wine glass.

The June 13 party took place at a six-bedroom rental home in South Bethany, Del., where Gansler’s son was staying with close to a dozen other graduates of the Landon School in Bethesda during “beach week.” Gansler said that his name was not on the lease but that he contributed to the rent.

He said that he faced the tensions facing any parent of a teenager: “How much do you let them go? How much do you rein them in? . . . I’m really no different from any other parent.” He said neither he nor his son was drinking.

Other photos and videos posted on social media from the party depict a wild environment at the house, with teenagers standing on a bar and perched on a banister in the main room as others dance below to Neil Diamond’s “Sweet Caroline.”

Gansler’s appearance at the beach party is the latest episode to detract from the fledgling Democratic primary campaign, in which Gansler faces Lt. Gov. Anthony G. Brown and Del. Heather R. Mizeur (Montgomery) in June.

Last week, The Washington Post reported that written accounts by the Maryland State Police alleged that Gansler regularly ordered troopers assigned to drive for him to speed and run red lights, even on the way to routine appointments. Gansler accused a police commander who documented those concerns of being a politically motivated “henchman” trying to help Brown’s campaign.

In August, before Gansler ­formally announced his long-
anticipated bid for governor, The Post reported that he was secretly recorded at a meeting with volunteers saying that Brown was relying on his race to get elected and that his campaign slogan was: “Vote for me, I want to be the first African American governor of Maryland.”

Gansler said Thursday that he remained undeterred by the controversies and was eager to talk about issues affecting Marylanders. He said he is a “a big boy” and understands the scrutiny that comes with running for governor. “We’re in it,” he said. “I’m going to win it.”

As attorney general, Gansler has taken on the issue of underage drinking. He appeared in a public- service announcement less than a year ago for the Century Council, a group that works to combat teen drinking. “Parents, you’re the leading influence on your teen’s decision not to drink,” Gansler said in the video. “It’s never too early to talk with your kids about smart ways to say no.”

Among other battles, he took on Pabst Brewing in a strongly worded 2011 letter. He and other attorneys general called for an end to a fruit-flavored, high-alcohol malt beverage that he said was packaged as “binge-in-a-can” and designed to appeal to young people.

And Gansler’s office got behind legislation this year to help prevent would-be underage drinkers from surreptitiously purchasing alcohol at a grocery store by checking out with a self-scanner.

Mothers Against Drunk Driving issued a statement Thursday saying that the group was “disheartened” to learn that Gansler may have attended an apparent underage drinking party. Gansler is considered a leader on the issue, the group said. It said that adults must “take the lead and make it clear to their children that drinking any alcohol before age 21 is both dangerous and illegal.”

The legal drinking age in Delaware, as in Maryland, is 21. According to Delaware state law, an adult who buys or gives alcoholic beverages to people younger than 21 or allows someone under his or her supervision to consume alcohol can be subject to a fine of up to $500 and sentenced to perform community service and serve up to 30 days in jail. But the law does not apply to family members within the private family home.

It is not clear how the law would apply to a rental home with chaperones and underage teenagers from many different families. A spokesman for Delaware’s attorney general said the office would not comment on hypothetical scenarios.

But Gansler told the Sun: “Assume for purposes of discussion that there was widespread drinking at this party. How is that relevant to me? . . . The question is: Do I have any moral authority over other people’s children at beach week in another state? I say no.

“My responsibility is only to my child,” Gansler added. “Everybody has their own moral compass. Mine is to raise my own child.”

He softened that at the news conference, which drew national media attention, acknowledging that he should have at least approached the chaperones to ensure everything was all right. He emphasized, however, that he did not witness anyone in danger or exhibiting signs of intoxication.

“I didn’t see anybody in front of me clearly in danger or in any risk,” he said.

Earlier on the night of the party, Gansler had appeared in Ocean City at an event sponsored by the Maryland Bar Association, according to his campaign.

Timothy Dickson, a Virginia man who owns the South Bethany beach house, said he is seeking a legal remedy for significant damage to the house that he said is believed to be connected to the tenants who stayed there during the week of the party.

Police have said the damage probably occurred during a break-in after tenants departed — a scenario that Gansler said Thursday was his understanding of what occurred.

At a town council meeting a few weeks later, damage at the property was said to be about $50,000, according to the minutes.

Dickson said he had forwarded to police some documents discovered in the home after the tenants left. They include a roster of the boys who stayed there that week and a list of parent chaperones throughout the week.

A “Doug” is listed as a chaperone on the Saturday and Sunday before the Thursday party, according to a copy of e-mails sent to parents that were obtained by The Post. Gansler’s attorney general e-mail address is among the recipients.

Gansler spokesman Bob Wheelock said Gansler never filled a chaperone shift. “He wasn’t a chaperone for those two nights or any other night,” Wheelock said.

Wheelock said Gansler, who was staying in another beach house in the area that week, dropped by the house where the teens were staying one night earlier in the week. Gansler might have had a beer that night with the chaperones on duty, Wheelock said.

Robert Lynch, a parent who was scheduled to chaperone the night of the June 13 party, declined to be interviewed by The Post on Thursday.

“If this is about the Doug Gansler thing, I’m not going to comment,” he said before hanging up the telephone.

A list of “2013 Beach Week Rules” included in the documents says that “no hard liquor or controlled substances may be consumed.”

The rules also note that “chaperones will record any DAMAGE to house and inform incoming chaperones. Damages will be discussed with boys as it happens, if blame can be placed on an individual, his security deposit will reflect damage.”

At Thursday’s news conference, Gansler was asked whether he was accompanied by a Maryland state trooper the night of the party.

Gansler hesitated, then said: “I may have, but I really, really doubt it.”

Susan Svrluga, Peter Hermann, Mark Berman, T. J. Ortenzi and Jennifer Jenkins contributed to this report.