The battle for Senate control finds Democrats trying to mount upset challenges in a string of typically Republican states, and this round of Battleground Tracker polls shows them having at best mixed results so far. In the closely watched race in Texas, incumbent Republican Ted Cruz has a lead over Democratic challenger Beto O’Rourke, at six points among likely voters, 50-44.

In Arizona — an open seat in a state that went for President Trump in 2016 — Democrat Kyrsten Sinema has a slight edge over Republican Martha McSally, 47-44.

Tennessee finds Republican Marsha Blackburn with an eight-point lead over Democrat Phil Bredesen, 50-42. Bredesen is a former governor who, having won statewide office before, has given Democrats hope of flipping a red state that Mr. Trump won easily.