SAN FRANCISCO -- Dwight Clark, who has the most famous fingertips in NFL history, concedes that even he felt overmatched when it came time to shake hands with President George H.W. Bush during the 49ers' visit to the White House in 1990.

Sure, Clark had made "The Catch" and was now coming off back-to-back Super Bowl triumphs as part of the team's front office. But you can't pull rank on the commander in chief.

"I'm not sure he knew who the hell I was, but that's fine," Clark recalled with a laugh last week. "He's the president of the free world."

Chances are that Bush knew exactly who Clark was. Besides being a legitimate sports fan, Bush had learned from his predecessor, Ronald Reagan -- The Gipper himself -- that rubbing elbows with championship sports teams was a public-relations gold mine.

Presidents as far back as the 1860s had welcomed occasional sports heroes to the White House or placed a congratulatory call to the winning locker room. But it was Reagan who made Washington, D.C., a must-stop photo op for all major teams that won a championship.

The Giants are happy to rejoin the tradition. On Monday they will renew acquaintances with President Barack Obama, who will salute the 2012 World Series champions, just as he did when the 2010 band of misfits put on spiffy clothes and filed into the East Room.

Obama will need some fresh material: Many of his best zingers last time were directed at bushy-bearded reliever Brian Wilson, who is no longer with the team. Maybe Obama can make a prolonged speech about the MVP catcher -- a Buster Posey fili-buster -- because the backstop missed the 2011 trip with an ankle injury.

"I'm excited. I've never been inside the White House," Posey said last week. "It should be fun. It's a great honor."

In 2011, the Giants presented Obama with a No. 44 jersey (in honor of the 44th president), a bat signed by the entire team and a custom-made glove.

The team is mum about what gifts it will be bearing this time except to say they will give Obama what he really wants: Willie Mays is making the trip again. The president and the Say Hey Kid are on such friendly terms that Obama whisked Mays to the 2009 All-Star Game in St. Louis aboard Air Force One.

"Very rarely when I'm on Air Force One am I the second-most-important guy there," Obama quipped during the Giants' last visit. "Everybody was just passing me by -- 'Can I get you something Mr. Mays?' "

Jokes aside, coaches, athletes and White House staff members who have been through the ritual say that the ceremony honoring sports champions is no mere publicity stunt. That's why the Giants are going out of their way to make it happen, flying to Washington on Sunday night after their game in San Francisco, spending Monday at the White House and then boarding a bus to Philadelphia in advance of Tuesday's series opener.

"All of that kind of dissipates when you're pulling up to the White House," Giants president Larry Baer said of the busy itinerary. "The players become little kids, as do all of us. There's an exhilaration and a sense that this is a big deal. You're not just walking into the White House to take a tour. You're walking into the White House to be honored by the president. And there's a big difference."

Historians trace the earliest recorded White House visit by a baseball team to 1865, when the Brooklyn Atlantic squad earned an audience with President Andrew Johnson after beating the National Club of Washington in an amateur game played on the White House grounds. (Brooklyn had "whipped our fellows pretty badly," Johnson told a reporter from The New York Times.)

The first World Series champs believed to be invited to visit the White House were, predictably the Washington Senators. A 2010 New York Times story recounted that President Calvin Coolidge was flooded with letters from fans imploring him to honor the hometown champs after the Senators won it all in 1924.

Coolidge, no baseball fan, held off until the following year, greeting the Senators shortly after they won the American League pennant -- and shortly before they lost the World Series.

Other presidents over the years have been enthusiastic sports fans, including Dwight D. Eisenhower, John F. Kennedy and, especially, Richard M. Nixon. Nixon was such a football fan that he once considered Vince Lombardi as a possible running mate -- before learning he was a Democrat -- and was known to offer up play suggestions to Washington Redskins coach George Allen.

Reagan, though, is the one credited with turning the sports photo op into an art form. An NFL Films retrospective on White House visits points to the 1986 celebration honoring the New York Giants as a seminal moment. Reagan invited the entire team, traded Gatorade baths with linebacker Harry Carson -- they were actually dousing each other with jugs full of popcorn -- and held up a Giants jersey with "#1 Gipper" on the back.

Now, as the website ThePostGame.com recently noted, every champion from the Super Bowl winners to Stanley Cup hoisters to NCAA women's lacrosse teams visits the White House for a final coronation.

Charles Bacarisse, who helped coordinate sports team visits for Reagan and the elder Bush, said such celebrations never got old, even when they became de rigueur.

"It gave a great break to the heavy conversations they have every day," Bacarisse said in a phone interview. "I think these are little moments of joy that presidents find in their daily schedule."

Bacarisse, an assistant director in the public liaison operation under Bush, helped arrange the 49ers' visit in 1990, and watched Bush schmooze with a star-studded roster that included Joe Montana, Jerry Rice, Roger Craig and Ronnie Lott.

Jerry Walker, the team's media relations director at the time, recalled that reserve running back Spencer Tillman nervously asked to be introduced to Bush, too.

"So I walked him over and said, 'Mr. President, this is ...' and before I could say it, President Bush said: 'Spencer Tillman. One of my favorite sportscasters.' "

Tillman had spent his offseasons working at a television station in Bush's native Houston. Now the lead studio analyst "College Football Today" on CBS, he said he still remembers what Bush told him during their brief exchange. "He whispered in my ear, 'Two things: Never take a picture with a drink in your hand and save 31 percent of whatever you make.'

"Being a fiscal conservative already, I kind of took that to heart."

Like his predecessors, Obama scored big points by showing off genuine sports knowledge. During the Giants' visit, Baer recalled the president making his way through a contingent that approached 200 people.

"This president is really, really good one-on-one, I've got to say," Baer said. "He was literally looking for everyone who had made the trip to Washington to make eye contact and say hello. So that was a thrill for people."

Occasionally, though, an athlete rejects the invitation to the White House in order to make a statement about politics -- or, in the case of Pittsburgh linebacker James Harrison, in order to make a statement about etiquette.

Harrison famously declined to attend the celebration after the Steelers' victory in Super Bowl XLIII, because he said the White House was merely jumping on the bandwagon.

"If you want to see the Pittsburgh Steelers, invite us when we don't win the Super Bowl," Harrison told Pittsburgh station WTAE-TV. "As far as I'm concerned, (Obama) would've invited Arizona if they had won."

Harrison also bailed on the Super Bowl XL ceremony hosted by George W. Bush.

Bacarisse, now the vice president for advancement at Houston Baptist University, said he understands that athletes have the right to dissent. Still, he is mystified why anyone would turn this one down.

"It's really a moment that can be celebrated, no matter who is in the White House," he said. "Of course, I appreciate and respect those who choose to make a statement by their absence. That's fine. But in effect, I think maybe they miss out."