Houston’s mayoral runoff, like all elections, will come down to turnout, but turnout variations may well point to a built-in advantage for one of the candidates.Senator John Whitmire received 43.0% of the vote in the November 7 election to Congresswoman Sheila Jackson Lee’s 34.8% in Harris Co., which represented 98% of all votes cast in the mayoral election. His margin was 8.2% or just over 20K votes. They each won about the same number of precincts over the other, but turnout within those precincts made all the difference.We looked at turnout at the precinct level from the November 7 election and conclude that Whitmire enjoyed a significant turnout advantage over Jackson Lee in that election.Looking solely at Harris Co., and excluding precincts with fewer than 20 votes cast, voter turnout was 25.0% in precincts favoring Whitmire and 16.0% in precincts favoring Jackson Lee. That gap widens when we look solely at precincts where either Whitmire or Jackson Lee received at least 50% of the vote. Turnout was 30.8% in precincts where Whitmire captured a majority vote but only 17.1% in precincts where Jackson Lee won a majority.Had voter turnout been equal and their relative vote percentages stayed the same, Jackson Lee would have finished first in Harris Co. with 41% of the vote to Whitmire’s 39%, a margin of around 6K votes.Also interesting is the relative strength of all other candidates in these precincts. Had all the other candidates been a single candidate, that candidate would have finished with a higher vote share than Jackson Lee in precincts won outright by Whitmire (23.6%-16.9%) and where Whitmire was south of a majority but ahead of Jackson Lee (28.7%-27.9%).In Jackson Lee’s strongest precincts, the opposite occurred: Whitmire finished ahead of the combined votes of everyone else. In precincts won outright by Jackson Lee, Whitmire received 17.1% of the vote compared to 10.8% for all other candidates. In precincts where Jackson Lee did not capture a majority but received more votes than Whitmire, he still eclipsed the other combined candidates (32.4%-26.0%).Higher precinct turnout correlates with higher vote shares for Republican candidates generally. Whitmire and Jackson Lee are both Democrats in this non-partisan race. Still, it may well be Republican-leaning voters who decide it unless Jackson-Lee’s campaign can overcome her turnout disadvantage.