Which way now, Lindsay Lohan?

Up until this weekend’s latest escapade, bad girl Lindsay Lohan was scheduled to spend the summer appearing in a bonanza of high fashion ads and marketing blowouts, culminating -- depending on your point of view -- in the horror flick “I Know Who Killed Me,” featuring Lohan in the dual role of troubled stripper and high school teenager, or in her 21st birthday party extravaganza at Pure nightclub in Las Vegas on July 2 and 3. Just last week, she was bragging to associates about the 500 guests scheduled to fly in for Lindsaypalooza.

And then came the Saturday morning tiff between her Mercedes and the bushes, which led to Lohan’s arrest on suspicion of drunken driving, with more charges possibly in the offing. Police have said that a substance believed to be cocaine was found. Since then it’s been hard to keep up with the gusher of sordid news and images circling the Internet -- a series of photos showing Lohan appearing sacked out in a car around 4 a.m. Monday (an AA sobriety necklace hanging from the rear-view mirror). Lohan’s representatives released a statement Tuesday that said she had checked into “an intensive medical rehabilitation facility on Memorial Day.”

Has a tipping point been reached? Now that she’s theoretically in line for a jail cell next to Paris Hilton’s, will the rats begin to scurry from the ship? Or is this a temporary blip in her celebrity?

Several calls and e-mails Tuesday to Lohan’s publicist, lawyer and mother went unanswered, and her manager declined to comment.

Undoubtedly, everyone who has signed on to the Lindsay juggernaut knew of her reputation -- her first stint in rehab, movie executives frustrated by her perceived lack of professionalism, the 24/7 partying dutifully chronicled by a platoon of paparazzi -- but still corporations were willing to gamble on her effervescent beauty.

Unlike fellow bad girls Hilton and Britney Spears, Lohan has high-fashion credibility. Two weeks ago, the most ubiquitous photograph from a Chanel fashion show in L.A. was Lohan looking radiant alongside the icon Karl Lagerfeld. Last week, black-and-white glamour photos of a topless Lohan in nothing but a miniskirt, lying amid rumpled sheets clutching a Jill Stuart patent leather satchel, made the rounds on fashion news sites and blogs. The photo was the first released from a print advertising campaign that the contemporary sportswear designer had planned to place in magazines starting in August.

Ron Curtis, Stuart’s husband and the company’s president, said the Lohan campaign is prominently featured in the window of their new East Hampton, N.Y., store.

“Before the incident this weekend, people were walking into our store saying, ‘How could you put that girl in your ads? She’s awful.’ Then, after her trouble this weekend, the same kinds of people were walking in and saying, ‘Oh, look at her, she looks so beautiful. She’s never looked better.’ It was bizarre. We live in a topsy-turvy world.”

Asked if the company would react to Lohan’s debacle in the same way major fashion brands backed away from Kate Moss, Curtis said, “No.”

“The lesson to be learned from Kate Moss was that she came back stronger and better than ever,” he said.

But Steve Levitt, president of Marketing Evaluation/The Q Scores, which evaluates celebrities for advertisers and licensers, says that consumers, according to their surveys, are turning off to Lohan. In the February 2007 study, Lohan’s negative ratings were “four times” her positive ratings, although “her recognition is up a lot.”

Lohan has already modeled for Prada’s Miu Miu spring-summer 2007 collection, appearing in print ads as a fashion-forward Raggedy Ann doll, with a mop of curly red hair, darkened eyebrows and scarlet lips.

It’s unclear if Lohan’s birthday party backers are going to be so resolute in her defense.

Even before this weekend’s arrest, Lohan’s upcoming bash at Pure had evoked eye-rolling, given the fact that Svedka Vodka was putatively sponsoring a fete for a girl newly released from rehab. The deal was to have netted her seven figures.

But last week, Mike Martin, a spokesman for Fairport, N.Y.-based Constellation Brands Inc., which owns the Swedish vodka brand, dismissed the story, saying, “It is not true that we are sponsoring her birthday party.” He did note that “her organization, if you will, has been in touch with us. There have been discussions. We are always looking at all kinds of promotions for various products.”

On Tuesday, a representative of Pure Management, which is actually orchestrating the various Vegas festivities, declined to say whether the party was going forward. “We think the world of Lindsay. We’re not going to touch on anything else,” said Kate Turner, Pure’s publicity person.

However, Benefit Cosmetics, based in San Francisco, a retro-cool cosmetics company known for its quaint paper-box blushes and bestselling Badgal Lash mascara, is still onboard to host the morning-after party. “We are still in talks to host Lindsay’s brunch,” said Sarah Reischman, publicity coordinator for Benefit. “As of right now, we believe that the party is still on.”

Others -- not already entwined in the Lohan brand -- are less sanguine about her future. “It’s difficult to know what is going to happen,” says Noreen Jenney, president of the Celebrity Endorsement Network, which helps corporations such as Johnson & Johnson book celebrities. “She didn’t have the best reputation when she got the [ads], and they still went with her.”

Jenney points out that it is standard industry practice to include a morality clause in contracts.

For the last two years, Lohan has been attempting to rehabilitate her Hollywood career, with seemingly savvy moves that would allow her to ease from child actress into leading lady. She appeared alongside Meryl Streep in Robert Altman’s last film, “A Prairie Home Companion”; in the indie ensemble film “Bobby”; and, most recently, as Jane Fonda’s troubled granddaughter in “Georgia Rule,” which is in theaters now. During the filming of the last movie, producer James G. Robinson publicly rebuked Lohan for tardiness and causing delays, although her performance -- a kind of riff on her own tabloid persona -- did end up with its admirers, among them film critic A.O. Scott of the New York Times. Still, the movie has earned only $16 million thus far, a far cry from the kind of grosses Lohan sparked in her teen hits “Freaky Friday,” which topped $110 million, and “Mean Girls,” at $86 million-plus.

Several Hollywood players who’ve worked with Lohan have expressed dismay that the young actress has alienated her core audience -- young girls -- with her behavior in the tabloids.

“She hasn’t been proprietary about her persona,” sighs one producer who knows her well and declined to be identified. “You don’t have to go to the movies to see Lindsay; you can go to the checkout stand to see Lindsay. When your personal life is bigger than what’s on screen, you’ve blown it as an actor.” Several pointed out that lax work habits are much more of a problem during a movie shoot, which requires months of work, than a fashion photo shoot, which can be accomplished in hours.

Says one who’s worked with her, “She did warn us that she’s better in the afternoons.”

Lohan’s next movie, “I Know Who Killed Me,” a drama-thriller, is still on schedule to premiere in Los Angeles on July 26, according to a representative of Screen Gems, the movie’s distributor.

A new movie about wayward grannies, starring Shirley MacLaine and Olympia Dukakis, has Lohan in a supporting role. The production company said Tuesday that it had extended shooting to accommodate Lohan’s expected stay in rehab.

rachel.abramowitz@ latimes.com

sheigh.crabtree@latimes.com

Abramowitz is a Times staff writer and Crabtree is a special correspondent.

Times staff writer Robert W. Welkos contributed to this report.