DALLAS — The first Hispanic female sheriff in Texas is headed to a Democratic runoff against the son of a former governor in their longshot bid to unseat Republican Gov. Greg Abbott.

Former Dallas County Sheriff Lupe Valdez and Houston investor Andrew White advanced Tuesday from a field of nine largely unknown Democratic primary candidates. The runoff election is May 22.

Texas Democrats haven't won a statewide race since 1994. The party's rising stars in Texas all passed on running for governor after Democrat Wendy Davis lost by 20 points in 2014.

White is the son of former Texas Gov. Mark White, who served one term in the 1980s and died last year. Andrew White is a self-described "conservative Democrat" who has alienated progressives over his personal opposition to abortion.

Valdez would be the first Hispanic and openly gay governor in Texas history.

Whoever wins the May runoff will face incumbent Republican Gov. Greg Abbott. Abbott easily clinched his party's nomination Tuesday and has a campaign war chest worth around $43 million, more than any gubernatorial candidate nationwide.