National Democrats celebrated the results.

"Pete GallegoPete Pena GallegoER doctor chosen to lead Hispanic Caucus 4 Texas GOP congressional primary runoffs to watch GOP candidate scores upset win in Texas state Senate runoff MORE's win in this primary is the worst nightmare for Congressman Canseco and House Republicans. Democrats now have the strongest candidate  — a former prosecutor — to go up against Congressman Canseco in this district that voted for President Obama in 2008," said one Democratic strategist. "The chances of Congressman Canseco coming back to Congress got a lot worse tonight."

The LCV also promised to stay involved in the race during the general election.

"Ciro Rodriguez lost because he is out of step with most Americans on building a clean energy future," said LCV Senior Vice President Navin Nayak. "We look forward to working with Pete Gallego in the months ahead."

The Hill rates this race a "toss-up."