Washington ? It didn’t take long for this troupe of ex-Expos to figure out they weren’t in Montreal anymore.

There was the sellout crowd of 45,596, jumping in place to celebrate each of the Washington Nationals’ runs in a 5-3 victory over the Arizona Diamondbacks on Thursday night, making ol’ RFK Stadium sway like it hadn’t for baseball in 34 years. There were the fireworks, before and after the game, and first place in the NL East.

And then there was the visit from the Commander in Chief.

President Bush walked into the Nationals’ clubhouse before throwing out the ceremonial first pitch. He shook hands with each player, and stopped at veteran reliever Joey Eischen.

“Eischen, right?” said Bush, a former owner of the Texas Rangers.

“He remembered trading me,” Eischen said, his eyes wide. “That was pretty cool. I was some Single-A punk he got rid of to get a major-league pitcher. It was gratifying.”

The whole evening just got better and better for the Nationals and their new fans, decked out in a sea of red caps with the same cursive “W” the Senators wore before leaving for Texas in 1971.

“It was amazing to see. Honestly, it was more than I expected. They lived and died with every pitch,” left fielder Brad Wilkerson said. “You know it’s going to be a great place to play.”

Baseball is all about getting home, and this was an all-day celebration of a team longing for stability and a city yearning for a tenant. The District lost two teams to other cities.

President Bush delivers the ceremonial first pitch prior to the Nationals-Diamondbacks game. The Nationals played their first home game in Washington on Thursday night and defeated Arizona, 5-3.

Baseball fans in Washington hadn’t been able to root, root, root for the home team in more than 12,000 days. And they made up for it Thursday.

They applauded the local high school band that opened the pregame ceremony about 1 1/2 hours before the first pitch. They applauded the high notes in the national anthem. And the flyover by military jets. And the introductions of everyone associated with the Nationals, right down to the assistant clubhouse manager.

“It’s a good sports town. Y’all’s baseball fans never left. The baseball team did,” Eischen said.

Even the visitors took note of the raucous support.

“Us, as players, we’re excited not to be playing in Montreal,” Arizona outfielder Luis Gonzalez said. “We had what — 40,000 or 50,000 people tonight? If we had been there, they’d have had 2,000.”

Indeed, the Expos averaged fewer than 9,400 fans in 2004, the last of a trying few seasons in Canada. First, the team was destined to be folded. Then, it was forced to play some “home” games in Puerto Rico. Even when Major League Baseball — which owns the franchise — decided to shift the Expos to the District, it took drawn-out negotiations with the city council to solidify the estimated $581 million deal that includes a to-be-built stadium.

“I think of everything we went through,” commissioner Bud Selig said. “The turmoil, the travail — it was all worth it.”

It sure felt that way to the players when Vinny Castilla’s triple rattled around in the right-field corner in the fourth inning, bringing home the Nationals’ first two runs in their new digs. The crowd cheered as if their team had won the World Series.

“I just looked at the fans,” outfielder Terrmel Sledge said, “and thought, ‘We finally have a home-field advantage.'”

Mets 4, Astros 3

New York — Jose Reyes’ speed keyed a three-run New York rally in the seventh inning, and the Mets defeated Houston for their fourth consecutive victory. Mike Matthews (1-0) pitched a scoreless seventh ining to earn the win. Mets reliever Roberto Hernandez retired Jeff Bagwell with the tying run at second base to end the eighth. Braden Looper pitched the ninth inning for his first save.