Voting centers are open from 7 a.m. to 7 p.m. Monday through Saturday and noon to 7 p.m. on Sunday. Early voting ends Dec. 5.
Several races are on the ballot -- including the City of Houston mayor.
A new poll shows that one mayoral candidate is in a better position than the other when it comes to the runoff.
The poll was conducted by the University of Houston, Houston Public Media and the Houston Chronicle.
The results are nearly identical to what was seen on Election Night with Sen. John Whitmire maintaining a 7-point lead over Rep. Sheila Jackson Lee in the race for Houston mayor.
"He's got about a 7-point lead, which is a significant number, especially when you've got a pretty fixed number of voters. Unless you can really expand the number of voters who go out to vote or really change the issues in terms of how you message it, it's really just a challenge to be able to overcome even a small 7-point lead like he's got," KHOU 11 political analyst Brandon Rottinghaus said.
Rottinghaus co-authored the poll and said it can be used for candidates to push voters to the polls. Less than 200,000 people are expected to vote in the runoff, a small number considering Houston's population.
Rottinghaus said one of the most interesting pieces of information that came out of the survey was how voters felt about an audio clip of Jackson Lee berating an employee.
"We found that SJL's audio leak effectively hurt her among younger women, and this is compelling because, this is a race where the female vote is split between SJL and John Whitmire, so her losing among a core demographic that might be very supportive of her is a serious problem in the race," Rottinghaus said.
He said even though Whitmire's lead is relatively strong, Jackson Lee will have to pull out all the stops to get her supporters to the polls.
Rottinghaus said that in past mayoral races, the first-place finisher in the general election has won every runoff since 1977.