The New York Times The dream of a “Blue Texas” has captured the imagination of Democrats for nearly a decade, and Beto O’Rourke has come closer than anyone to making a statewide victory a reality. His strengths as a candidate in his narrow loss in a 2018 Senate race against Ted Cruz — by 2.6 percentage points — led his supporters to push him to run for president, and he obliged them Thursday morning. But his performance may have demonstrated something else: Texas is on the doorstep of emerging as a battleground state, and any number of Democrats might stand a chance to compete there in 2020 for the presidency or the Senate. His relatively close loss is promising for the party because he did not take full advantage of the longer-term trends that might put it over the top sooner than later. His strength came almost exclusively from white voters, not from the growing Hispanic population in the state. None of this is to take away from his accomplishment. He did better than every Democrat running statewide in Texas in the 2018 midterms. It seems unlikely that many Democrats would have fared as well as he did, and you could argue it bodes well for his chances in a presidential race. But on balance his success was a reflection of deeper trends. Mr. O’Rourke’s close result wasn’t because of an exceptional turnout that will be hard for other Democrats to repeat in 2020. Republican voters, defined as those who have participated in a recent Republican primary, turned out at a higher rate than Democratic ones. Neither the Hispanic nor youth voter share of the electorate was higher than it was in 2016, when President Trump won the state by nine points. On the contrary, Democrats in 2020 can be expected to enjoy a more favorable turnout because presidential races tend to draw in more young and Hispanic voters. Mr. O’Rourke might have won Texas last November if turnout had been at the level of a contested presidential race, based on an Upshot analysis of Times/Siena poll responses, actual results and voter file data from L2, a nonpartisan voter file vendor. The data yields an estimate of how every registered voter in Texas would have voted, based on a long list of geographic and demographic factors that predicted vote choice in the Times/Siena polling. Importantly, turnout in 2018 is among those factors, which allows us to fully untangle how much of Mr. O’Rourke’s strength was because of strong turnout among his supporters. The data indicates that two opposing turnout trends influenced the results. The electorate was older, whiter and more Republican than the state as a whole — or than the 2016 electorate. But an O’Rourke supporter was generally likelier to vote than a demographically and politically similar supporter of Mr. Cruz. This was the pattern nationwide, so it is not obvious that this can be attributed to Mr. O’Rourke specifically; it could have been the favorable Democratic environment more generally. Either way, the extra turnout boost probably cut Mr. Cruz’s margin of victory by two points. Mr. O’Rourke might have won with a turnout of around 10 million voters. (The actual turnout was around 8.4 million.) Without the extra edge of a Democratic wave year, it might have taken 11 million votes, a number that is not out of the question in 2020 if Texas is contested as a battleground state. So how did Mr. O’Rourke fare so well? He did it through old-fashioned persuasion, by winning voters who had voted for Republicans and for minor-party candidates. The results themselves make it clear that he won a lot of voters who supported Republicans in other races. He ran three points ahead of the overall Democratic state vote for the U.S. House in 2018 (adjusted for uncontested races), and ahead of every down-ballot Democrat running statewide. Mr. O’Rourke’s personal appeal was probably a factor, and there