Lupe Valdez advanced despite losing the support of some Hispanic activists over her record on immigration and will be a heavy underdog against Republican Gov. Greg Abbott in a state that hasn't elected a Democrat for governor in nearly 30 years.
Valdez's victory over Andrew White, the son of a former Texas governor, was among a small slate of primary runoffs that unfolded with little fanfare in Texas, which remains shaken by a high school shooting that killed 10 people just as early voting ended last week.
National Democrats were closely watching a congressional runoff in Houston and whether a liberal outsider who founded an activist group against President Donald Trump could advance to November with control of Congress on the line.
Laura Moser had forced a runoff in March after finishing second to Lizzie Pannill Fletcher, a former Planned Parenthood member who the Democratic establishment viewed as their only chance of flipping a district that Republican John Culberson has held since 2001.
It was one of three House primary runoffs in Texas that are key to whether Democrats can flip can the minimum 24 GOP-held seats they'll need to seize a majority in Congress next year.
Not willing to take any chances, the fundraising arm for congressional Democrats worked to undercut Moser in a district that has shifted from a Republican stronghold to a more Hispanic, better educated battleground that Hillary Clinton narrowly won in 2016.
Moser made the runoff despite the Democratic Congressional Campaign Committee criticizing her for writing jokingly in 2014 that she'd rather have teeth pulled than live in small-town Texas.
Susan Wright, a voter in Houston, said she thought "Democrats in Washington really screwed up" by attacking Moser.
"It was too bad they decided to make it sound like someone has done a big investigative report on her. I never saw it." Wright said.
Guns did not appear to be a late breakthrough issue in the runoff days after the shooting at Santa Fe High School outside Houston. Hours before polls closed Tuesday, Abbott hosted the first of three round table discussions this week with policymakers to discuss better fortifying schools.
But Abbott hasn't mentioned gun control and Democrats say Texas Republicans - who have a dominating majority in the state Legislature - won't dare cross the National Rifle Association by considering tighter firearm limits. Their party's candidates generally agree on gun control and there hasn't been much debate so far in the runoff races.
Two other Texas districts Democrats hope to flip are Dallas U.S. Rep. Pete Sessions', which supported Clinton instead of Trump, as did Rep. Will Hurd's, encompassing 800 miles of Texas-Mexico border from San Antonio to El Paso. Former NFL linebacker Colin Allred is expected to advance Tuesday to face Sessions and Air Force veteran Gina Ortiz Jones advanced to take on Hurd.
MEET THE CANDIDATES: LUPE VALDEZ