AUSTIN, Oct. 18 -- In a state with a lot more Republicans than Democrats, the Texas Senate race between Ken Paxton and James Talarico has been reduced to a plain question: who actually shows up. Early voting opens Monday, and the latest CBS News poll calls the contest essentially tied.

Talarico, a Democratic state representative, leads Paxton, the Republican attorney general, 51 percent to 49 among likely voters in the CBS News/YouGov survey, a gap inside its 3.5-point margin of error. The same pollster's Battleground Tracker poll put Democrats at 228 House seats in September, so Texas is now being measured against a national mood that has already moved.

Turnout is where it could break. Among registered voters, 87 percent of Democrats s...