Langston, who entered Texas with a slim two-point lead in the standings, posted a second in the opening moto and then followed it up with a convincing win in moto two to gain the overall victory. Honda's Andrew Short finished third overall on the day with a 1-5 moto finishes and now trails Langston by eight points in the AMA Motocross class standings.
KTM's Mike Alessi was second on the day (3-2) but lost ground on Langston and now sits 15 points behind in fourth. Kawasaki's Timmy Ferry finished fourth overall (4-3) and is third in the championship chase with a 13-point deficit.
The championship is still wide open with 50 points available at the final round next weekend in San Bernardino, California.
"The points lead is so tight and I knew I needed to win to take control of the championship," said Langston, who notched his 11th career AMA National win. "Obviously I got a little extra cushion [but] it doesn't change any strategy. I like Glen Helen. I've always done well there. I'm definitely looking forward to it and hopefully I can finish this off and win a championship."
Kawasaki's Ryan Villopoto picked up his fifth win of the season in AMA Motocross Lites at the inaugural race at Freestone County.
Villopoto turned in two near-perfect rides en route to a 1-1 sweep of the motos. He has six overall victories on the season, but more importantly, he now holds a 19 point lead over team-mate Ben Townley. A crash in the fist turn of moto one hurt Townley's title chances, and ultimately led to a 6-2 finish, earning third overall on the day but losing valuable championship points to Villopoto.
"It was a tough day," explained the former MX2 world champ. "I got a great jump out of the gate in that first moto and thought it was going to be on but it didn't turn out that way. I was looking for some wins today but I made a mistake in the back on the first lap and had to start from last and work my way up, so the first moto wasn't too good. I got a good start in the second one and got out behind Ryan pretty quick but I just didn't have anything for him. It was a big pay day for points but I just struggled really with small mistakes."
Yamaha's Broc Hepler finished second overall with a solid 3-3 performance.