The President, who turns 61 on Friday, took in the Cubs-Nationals game from the owner's box with team president Stan Kasten and general manager Jim Bowden on his right and left side, respectively.
Bush's visit went unannounced to the crowd, and the rest of his visit was kept just as private. He entered through a curtained gate after security officers cleared the hallway, and both Kasten and Bowden declined to comment on their time with America's First Fan.
During the game, Bush remained leaned back in his seat, and carried on conversations with Kasten, Bowden and Nationals principal owner Mark Lerner. He applauded a Nationals rally in the sixth inning and stood for the seventh-inning stretch before leaving the game. He saw all the runs that were scored as the Cubs defeated the Nationals, 4-2.
"It's pretty cool to look up there and see him," catcher Brian Schneider said. "Hopefully that's not the last time he comes."
He won't have many more opportunities to visit RFK, which will be replaced with a new ballpark in 2008. President Bush has been to four games since the Nationals arrived in 2005, with the team winning twice and losing twice.
None of the players or coaches got the opportunity to meet Bush, who arrived in the middle of the first inning. Manager Manny Acta has spent time with him before, and could tell something was up.
"You know how I knew he was here?" he asked. "It was the sharpshooters."
A full security detail was on hand to encircle the stadium, including officers standing on the platforms that hold the stadium lights. Nationals pitcher Jason Bergmann spotted them during his outing, and was glad Bush came on his night to throw.
"It was a great surprise, and an honor to pitch in front of him," Bergmann said.
The president is known as a baseball fan, and owned a share of the Texas Rangers for nearly a decade. While flying on Air Force One, he has his satellite televisions tuned to baseball games. He recently spent time with Detroit pitcher Justin Verlander while the team was in Washington. Verlander threw a no-hitter on June 12.
First baseman Dmitri Young was on hand in 2001 when Bush threw out the first pitch to open Miller Park in Milwaukee. He joked about the President's spotty attendance at RFK.
"About time he made it to a game," Young said.
While Bush's love for baseball is open knowledge, his visit to RFK Stadium on Thursday remained a secret. Even fans who were looking for him wouldn't have had much of a view -- the only thing they would have seen was the Aquafina bottle he had rested on the ledge in front of him.
That bottle was the only transparent part of the President's visit.
Michael Phillips is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.