WASHINGTON — There was no late-game meltdown by the Mets this time, no real reason to point fingers at the relievers. This was a start-to-finish loss, New York’s third loss in four games, and there will be no escaping the references to September 2007 now.

Washington’s John Lannan limited New York to one hit over seven innings, Anderson Hernandez delivered a two-run single off a tiring Pedro Martinez, and the Nationals beat the fading-again Mets 7-2 last night.

The Mets’ lead over idle Philadelphia in the NL East fell to a half-game; New York held a 3.5-game cushion as recently as Wednesday. The Mets have 13 games left, Philadelphia has 12.

Last season, the Mets led the Phillies by seven games with only 17 to play before a historic collapse ceded the division title and kept New York out of the playoffs altogether.

“It’s, unfortunately, just a part of who we are, as long as we’re in a race and competing,” Mets manager Jerry Manuel said before the game. “Until we win it or get into the playoffs, that’s something we have to deal with.”

Trailing 7-1 yesterday, the Mets threatened to make things interesting once Lannan (9-13) left the game. The rookie left-hander gave up a double in the third to Brian Schneider, who wound up scoring on Jose Reyes’ RBI groundout — and that was it. New York’s nos. 3-5 hitters — David Wright, Carlos Beltran, and Carlos Delgado — went a combined 0-for-11 with four strikeouts on the night.

It was quite a contrast to Lannan’s previous outing, also against the Mets: He allowed five runs and eight hits in three innings.

Garrett Mock entered for the eighth and immediately gave up Luis Castillo’s double, a walk and Reyes’ RBI single. Mock was replaced by Mike Hinckley, and Ryan Church greeted him with a single that loaded the bases.

That brought up Wright, he of the 31 homers and 114 RBIs and MVP candidacy. But Hinckley got him to ground into an inning-ending 6-4-3 double play.