By the Numbers: First-place Candidates in Runoffs

82%

Winning percentage of runoff candidates who finished 10% or more ahead of their challenger in the primary election since 2002.

There have been 175 “open” primary runoff elections for state, legislative and federal offices since 2002, and the candidate who finished first in the primary election has won exactly 60% of them. “Open” runoffs do not have an incumbent on the ballot.

As we did in 2018, we looked at the winning percentages of first-place candidates based on whether they received more or less than 40% of the vote in their respective primaries and whether they finished more or less than 10% ahead of their rival. The 2018 results tracked very closely with the historical averages. Since 2002, first-place candidates won:

• 80% of runoffs after receiving at least 40% of the vote with a margin of at least 10%
• 89% of runoffs after receiving less than 40% of the vote with a margin of at least 10%
• 52% of runoffs after receiving at least 40% of the vote with a margin of less than 10%; and
• 43% of runoffs after receiving less than 40% of the vote with a margin of less than 10%.

There’s something particularly interesting about this final category. Democrats won 67% of their runoffs after receiving a plurality under 40% and a margin below 10 points, and similarly situated Republicans won only 32% of the time.

First-place candidates’ historical success rates increase as their plurality rises:

• 74% of candidates receiving at least 45% of the vote prevailed
• 65% of those receiving 40%-45%
• 56% of those receiving 35%-40%
• 50% of those receiving 30%-35%; and
• 45% of those receiving less than 30% of the primary vote.

The same applies to their margin over the second-place candidate:

• 89% of candidates finishing more than 20 points ahead of their rival prevailed
• 83% of those finishing 15-20 points ahead
• 79% of those finishing 10-15 points ahead
• 48% of those finishing 5-10 points ahead; and
• 44% of those finishing less than 5 points ahead in the primary.

Of those who finished less than 5 points ahead of their rivals, 62% of Democrats prevailed compared to 36% of Republicans.

We are seven weeks away from runoff election night when voters will decide the outstanding Republican and Democratic nominees for federal, state and county office. We are tracking 33 of those races for Congress, statewide office and the Texas Legislature, and have broken them down into four categories based on the first-place candidate’s plurality (over or under 40%) and their margin over the second-place finisher (over or under 10%). Keep in mind that the winning percentage is the historical average, not any one candidate’s odds of winning their particular race.

Runoffs involving incumbents are a different story. Six legislative incumbents were forced into a runoff this year:

• SD27 (D): Sen. Eddie Lucio Jr. (49.8%) vs. Sara Stapleton Barrera (36%)
• HD2 (R): Rep. Dan Flynn (45%) vs. Bryan Slaton (36%)
• HD59 (R): Shelby Slawson (46%) vs. Rep. J.D. Sheffield (30%)
• HD100 (D): Rep. Lorraine Birabil (29%) vs. Jasmine Crockett (26%)
• HD142 (D): Rep. Harold Dutton (45%) vs. Jerry Davis (25%)
• HD148 (D): Rep. Anna Eastman (42%) vs. Penny Morales Shaw (22%)

Since 1996, 28 incumbent legislators have been forced into runoffs, and 23 of them have lost. All five who prevailed finished first in the primary election, and four of them received at least 17 points more than their opponent in the primary election. At least 10 straight incumbent legislators who finished second in the primary election went on to lose the runoff election.

Sheffield faces the greatest negative primary margin (-15.7%) of any legislative incumbent forced into a runoff since 1996. His 30% vote share is also the lowest for any incumbent who advanced to a runoff in that period.

Early voting for the July 14 runoff election begins June 29.