WASHINGTON - The tradition began on April 14, 1910, when William Howard Taft threw a ceremonial first pitch at a Washington baseball game between the Senators and Athletics.

Exactly 95 years to the day - and after a drought of more than three decades - the president will again launch a season of the national pastime in the nation's capital tonight when the Washington Nationals host the Arizona Diamondbacks in the city's first home opener since 1971.

The honor this time around goes to George W. Bush - with the "W" written in curly script on the scoreboard, mimicking the design on the Nationals' hats. It's a seemingly appropriate role for a chief executive who was once a part-owner of the Texas Rangers.

"He's loosening up and getting ready," White House press secretary Scott McClellan said Wednesday.

That's promising news for Nationals catcher Brian Schneider, who doesn't want to bobble the presidential pitch amid the excitement and nerves of a historic night expected to pack some 46,000 people into RFK Stadium.

"I'm looking for that thing to come right down the middle," Schneider said. "I know he can do it."

Bush becomes the 12th president to throw out a first pitch in Washington and the first since Richard Nixon in 1969. After the Senators left, presidents performed the ceremony in other cities; Bush did the honors in St. Louis last year.

There already have been numerous milestone dates to celebrate baseball's return to Washington, which had been without a team since the expansion Senators departed for Texas 34 years ago. There was the announcement on Sept. 29 that the Montreal Expos were relocating here, followed by the opening of spring training and the first spring training game in February, an exhibition game at RFK on April 3, and then the season opener at Philadelphia a day later.

This is the last of the welcome-back parties, but it's also the biggest.

Tickets have been hard to come by, even for some well-heeled Washingtonians. The day starts with a Welcome Home luncheon for the team, and there are 95 minutes of pregame ceremonies scheduled before the 7:05 p.m. start time. Ten former Senators will be on hand, including Joe Grzenda, who threw the last pitch at the last game in 1971 and will hand the ball from that game to Bush for the presidential first pitch.

"We know it's going to be a long day," pitcher Zach Day said. "But everybody's excited for the day to come."

The Nationals are the last team to play a home game this season, which is probably for the best given the compressed schedule for renovating the stadium. Hundreds of extra chairs were being set up on the field in front of the stands late Wednesday, the sort of additional seating used for World Series games. Mowers trimmed the grass, and were hoping to find a way to get rid of the faint white lines still visible from a Major League Soccer game last week.

Perhaps the biggest surprise is that the Nationals arrived as a first-place team, having won two out of three against the Atlanta Braves to improve to 5-4 in the NL East. Washington is playing with much of the same roster that finished last in 2004 in Montreal, although the players are finding they have much greater fan support than they had in Canada.

"We expect a lot of excitement. The fans are going to show up and root for us," third baseman Vinny Castilla said. "They've been waiting for this for a long time."