(from left): U.S. Rep. Beto O'Rourke (D-El Paso) and U.S. Sen. Ted Cruz (R-Texas). Credit: Rodolfo Gonzalez: O'Rourke/Marjorie Kamys Cotera: Cruz

In his race against U.S. Sen. Ted Cruz, Beto O’Rourke is vying to be the first Democrat elected to a U.S. Senate seat in Texas in 30 years.

U.S. Senate terms last six years. Their terms are staggered so neither seat is up for election at the same time. Texas is currently represented in the U.S. Senate by John Cornyn and Cruz.

Texas was a solidly Democratic state for decades. The state’s shift to Republican began in 1961, when John Tower won a special election for U.S. Senate, becoming the first Texas Republican elected statewide since Reconstruction.

For the next three decades, Texas had both a Democrat and a Republican representing the state in the U.S. Senate. The Republicans that followed Tower were Phil Gramm, Kay Bailey Hutchison, Cornyn and Cruz.

Lloyd Bentsen was the last Democrat elected to the U.S. Senate from Texas in 1988. Bentsen originally won the seat after defeating incumbent Yarborough in the Democratic primary in 1970.

Chris Essig builds data visualizations and news apps at the Texas Tribune. Before joining the team in February 2017, Chris spent almost six years in Iowa, including two and a half years as a developer...