Early election results showed Menefee with a strong lead over Green, gaining more than 70 percent of votes, according to the Associated Press, which called the election right before 8:00 p.m. Tuesday night.
But Republican-led redistricting later forced Menefee and Green into the same newly redrawn district, setting up one of the most closely watched Democratic runoffs in Texas.
The runoff became one of the most closely watched Democratic races in Texas after Republican-led redistricting dramatically reshaped Houston-area congressional boundaries, effectively forcing two incumbent Democrats into the same district.
Throughout the race, Menefee campaigned as a newer generation of Democratic leadership focused on legislative strategy, government accountability and direct legal fights against the Trump administration.
The geographic divide inside the district also became a defining feature of the race. Menefee dominated Harris County during the March primary, while Green performed strongly among Fort Bend County voters.
His victory Tuesday in the Democratic runoff is heavily favored to win the November general election in the safely Democratic district.