They play a postponed MLS match three days later at the same venue, with the All-Star break to follow, after which the real push for the playoffs begin.
Houston, which drilled Atlante, 4-0, in its SuperLiga opener last weekend, can advance with a tie to the SuperLiga semifinals; D.C., with two losses in two games, not only must win, it must win big to have any chance of moving on.
In SuperLiga play Tuesday night, Omar Arellano scored the only goal as Guadalajara (2-0) beat Houston, 1-0. Chivas leads Group A with six points. Houston is tied for second with Atlante; both teams are 1-1 after Atlante rebounded from its thrashing at Robertson Stadium last weekend to down D.C., 3-2, at RFK with a pair of goals by Luis Gabriel Rey and one from Christian Bermudez.
Goal difference will separate ties in the standings if Guadalajara wins the group and the other three teams wind up with three points, or if Atlante and Houston win and three teams finish level on six points. If D.C. beats Houston by three goals or more, it can reach the semifinals assuming Guadalajara defeats its Mexican League rival.
Francis Doe equalized for D.C. after Rey opened the scoring in the 15th minute, but not for the first time this season, United conceded a goal at a critical juncture when Rey struck again just before halftime. Bermudez upped the lead to 3-1 early in the second half and despite Luciano Emilio's goal in the 79th minute and several subsequent chances D.C. fell short.
Houston, missing Dwayne De Rosario because of suspension and Brian Ching and Stuart Holden to injuries, was thwarted by Guadalajara keeper Luis Ernesto Michel several times and then committed a mistake in the 71st minute that broke open the goalless deadlock.
Defender Pat Ianni overran a ball in midfield and Arellano sped away to stroke a shot past keeper Pat Onstad.
The Dynamo played in front of 28,723 fans, the fourth-largest crowd in its history since moving to Houston from San Jose prior to the 2006 season. United drew less than half that figure, though the announced crowd of 12,122 made a lot more noise than the numbers might suggest.