WASHINGTON (AP) — Call it the Obama effect: A presidential visit can be good advertising for restaurants and businesses.

Vermilion in Alexandria, Va., is one of the most recent establishments in the spotlight after President Barack Obama and his wife, Michelle, dined there on Valentine’s Day.

“That kind of exposure has helped drive business without a doubt,” general manager David Hammond said. “A lot of our regular diners have been congratulatory. There’s a real positive buzz.”

While the contemporary American restaurant — which changes its menu weekly based on local and seasonal availability — would not reveal what the Obamas ate, the special four-course menu for the holiday included grass-fed beef “tartar,” Chesapeake rockfish and chocolate truffle tart.

It’s not just restaurants that experience the Obama effect.

After the first family visited the Corcoran Gallery of Art in January, “we definitely saw a spike in all areas including Web traffic, press interest and foot traffic,” museum spokesperson Rachel Cothran said.

The Obamas viewed “30 Americans,” which featured artwork by African-Americans, and a collection of Civil War photographs.

Interest in where and what Obama and his family do can be explained with one word: authenticity, according to George Washington University Professor Larry Parnell, who directs the school’s strategic public relations program and formerly advised politicians and corporate chief executives.

Parnell said Americans can relate to Obama stopping at a burger joint, filling out sports brackets and shopping at Petco with his dog. It also helps that he has heralded the White House as the “people’s house” and talked of bringing the community to the Executive Mansion since the beginning of his presidency, Parnell said.

“It’s a sense of him being authentic and real,” Parnell said. “It’s who he is as a person, and Clinton, to the same extent as well, had the ‘everyman’ element as well. They can relate to the average person.”

Parnell said Obama, like Bill Clinton, may appeal to Americans because of his humble background and upbringing with close community roots. He said Republican president hopeful Mitt Romney may struggle with this.

But the GOP frontrunner has already taken advantage of this approach, visiting Charlie Parker’s Diner in Springfield, Ill., for pancakes and omelets while campaigning in March.

Diner own Mike Murphy said Romney’s team approached him in advance of the visit.

“Every day since then, we’ve had people inquire about it,” Murphy said. “I imagine that will happen for a long time and even longer if he happens to become president.”

In fact, Murphy said he’s asked at least a dozen times a day about Romney’s visit, which is enshrined in a photo of both men and their wives displayed near the diner’s cash register.

However, Romney’s unscheduled stop in April at a Culver’s burger place in Johnson Creek, Wis. — where he gave out a round of handshakes as he picked up takeout — was mostly unnoted.

But a visit from the commander in chief is often marked with swelling crowds and flashing cameras.

Parnell says Obama simply has the “touch.”

“You can’t manufacture it; either you have it, or you don’t,” he said.

The Obamas have made their way onto the menu at Good Stuff Eatery, a Capitol Hill restaurant specializing in burgers and shakes.

Good Stuff started serving an Obama burger to compete against a John McCain burger during the 2008 presidential election campaign.

“It was kind of a play on what the people wanted,” marketing director Jordyn Lazar said.

The Southwest-flavored McCain burger lost to what would eventually become the Prez Obama Burger, a bacon cheeseburger with onion marmalade and horseradish mayo sauce. Lazar said it’s the eatery’s best-selling burger.

Capitalizing on the charm, Good Stuff also started dishing out in 2010 the Michelle Melt: a turkey burger with lettuce, tomato, cheese, caramelized onions and “Southlawn Herb Garden Mayo” on a wheat bun.

The Obamas not only popularize entrees but have the ability to boost sales across the country on their vacation stays, from Martha’s Vineyard to Hawaii.

The family has stopped in Bunch of Grapes bookstore in Vineyard Haven, Mass., for the past two summers, purchasing books such as the classic “To Kill a Mockingbird” to the Pulitzer Prize-winning “Tinkers.”

“The days following anytime he visits, we have a huge increase in sales,” owner Dawn Braasch said. “I’m not sure why it is, but it is. I don’t know if people think he will come back and they will get a glimpse.”

The store, carrying more than 50,000 books, has also hosted Secretary of State Hillary Rodham Clinton and her husband, former President Bill Clinton, for their book signings.

During Christmas breaks in Hawaii, the Obamas have collectively stopped in Island Snow at least a half dozen times for shave ice. The president was also photographed wearing an Island Snow T-shirt on the beach.

Store president James Kodama said Obama’s stay in the little town of Kailua has promoted awareness of the entire beach community. It’s also increased foot traffic for his shop that sells beach and surf apparel.

The family always stops to take pictures with the staff and once invited some of the employees to their send-off at Hickam Air Force Base, he said.

“I know people come to our store because he was here,” Kodama said. “People are kind of wondering if he’s stopped by and they are chancing it.”

But more than curiosity lures customers in. Andrea Morales, associate professor of marketing at Arizona State University’s W.P. Carey School of Business, said an implicit recommendation from a public figure is more effective than an endorsement from a paid celebrity spokesperson.

“Just being photographed and saying ‘this is good’ carries a lot of weight and, in fact, carries more weight because they think ‘you’re not getting paid to say that you just like this place,’” she said. “That type of marketing, even though it’s not mainstream or not the typical marketing, has become more effective.”

Morales said consumers may ask where Obama sat because of a positive consumer contagion, or they believe “there’s some trace of him left there” that they want to experience themselves.

Ben’s Chili Bowl in Washington’s popular U Street corridor still draws patrons asking what Obama ate and where he sat when the then-president-elect visited the restaurant before his inauguration in January 2009.

“It’s been tremendous, the response, since he’s been here, and it really continues to this day,” co-owner Nizam Ali said.

He said business from the first family has a broader impact on the community.

“It’s been tremendous for every local business he has patronized and very helpful to the D.C. community as well,” he said. “It did kind of symbolize that he and his family would be Washingtonians and enjoy the city as residents. This is his community now.”

Copyright 2012 The Associated Press.