Given the following reasoning and answer, what was the question? The important part for answering this question is: 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.
The answer: Lupe Valdez
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?