 
<translate> Tambayar tambaya: Za a gudanar da zaɓen gwamnan Texas na 2018 a ranar 6 ga Nuwamba, 2018, don zaɓar Gwamnan Texas, tare da zaɓen kujerar Majalisar Dattawa ta Amurka ta Texas, da kuma sauran majalisun majalisa, jihohi da na gida a duk faɗin Amurka da Texas. Gwamnan mai ci na Republican Greg Abbott yana neman sake zabarsa zuwa wa'adi na biyu a ofis kuma zai fuskanci Democrat Lupe Valdez, tsohon Sheriff na Dallas County, da kuma Libertarian Mark Tippetts, tsohon memba na Lago Vista majalisar gari.  Tambaya: Bisa ga wannan nassi, su waye 'yan Democrat da ke neman kujerar gwamnan Texas? <eng> The question Passage: The 2018 Texas gubernatorial election will take place on November 6, 2018, to elect the Governor of Texas, concurrently with the election of Texas's Class I U.S. Senate seat, as well as other congressional, state and local elections throughout the United States and Texas. Incumbent Republican Governor Greg Abbott is running for re-election to a second term in office and will face Democrat Lupe Valdez, the former Sheriff of Dallas County, as well as Libertarian Mark Tippetts, a former member of the Lago Vista city council.

Question: Based on this passage, who are the democrats running for governor of texas? 