Voters in the fast-growing Houston suburbs will offer a rare glimpse into a critical segment of the electorate on Tuesday when they elect a new state representative, in what could prove an early bellwether ahead of the 2020 presidential elections. The district leans Republican; President Trump took 53 percent of the vote there in 2016, and Sen. Ted Cruz (R) won it by 3 points in 2018. But the race to fill a seat that became vacant when the Republican incumbent, state Rep. John Zerwas, left to take a university job has become a magnet for outside Democratic groups who...