A formula you say? There's a formula for a blue Texas? Well, sort of. I mean this in the sense that a sober quantitative accounting of the challenge Democrats face in Texas provides a useful guide to how the blue Texas goal can actually be attained. More useful I think than the countless breathless accounts of grassroots Democratic organizing in Texas (here's a recent example), which make little effort to explain which groups have to move and by how much to be successful.
So here's the "formula". In 2016, Clinton improved over Obama in Texas, reducing his 16 point deficit in the state to 9 points in 2012. How did she do this? The dataset developed at CAP for our Voter Trends in 2016 report indicates that Clinton improved over Obama among both white non-college-educated and college-educated voters. The Democrats’ deficit among Texas’s white non-college-educated voters fell from 60 points in 2012 to 55 points in 2016. The shift toward Clinton among white college graduates in the state was even larger—from a 30-68 percent deficit in 2012 to 37-57 percent in 2016, a margin improvement of 18 points. The white college-educated improvement cut Clinton’s deficit in the state by about 4.5 points and the white noncollege improvement moved things in her direction by about 1.5 points, for a total shift of 6 points toward Clinton from better performance among whites. The rest of Clinton's gains relative to Obama were accounted for by improvements in Latino turnout and support.
This suggests that the correct formula for a blue Texas is not to rely on demographic change and better mobilization of existing pro-Democratic constituencies, which often appears to be the default strategy. That is not likely to be enough to cut the additional 9 points off of Democrats's statewide deficit anytime soon. Instead, while demographic change will continue to provide a boost to Democratic prospects and mobilization efforts should continue, the key question is how to keep the trends evident in 2016 going. Rough calculations indicate that if Democrats can cut their white noncollege deficit to 45 points and their white college deficit to 10 points, while continuing positive, if unspectacular, Latino trends (getting Latino turnout of eligibles to around 40 percent, while improving Latino vote margin to around +30D), that should be enough to flip the state or come very close.
Note: I'm not saying this would be easy to do! But I do believe the formula would work and builds plausibly on current trends.