They see the rise of the Latino population in the state - and the group's traditional adherence to the Democratic Party - as giving them a democgraphic edge over Republicans.
From an NYT analysis:
Texas is ripe for realignment. Insofar as demographics count, Texas is on a path to first turn purple and then blue. The question is when. Whites are already a minority of the state’s population, 44.8 percent, down from 52.4 percent in 2000; blacks are at 12.2 percent, slightly up from 12.0 percent; Hispanics are at 38.1 percent, up from 32.0 percent; with Asian-Americans, Native Americans, and others making up the remaining 4.9 percent. Whites are teetering at just over 50 percent of Texans eligible to vote; according to demographic projections, they will become a minority of voting age citizens in 2016.
What makes Texas such an inviting target for Democratic organizers is that Hispanic turnout in the state is strikingly low, 38.8 percent of those eligible to vote, compared to the national average of 48 percent.
Even if Latino turnout in Texas increases to the national average, Democrats will be unable to win statewide in the short term, but the long term they may well.