John Cornyn lost the Texas GOP Senate primary runoff to Ken Paxton on May 26 and 27, 2026. Cornyn and his allies spent roughly $100 million, and up to $128 million according to AdImpact, on ads aimed at defeating Paxton. The effort ended Cornyn's Senate career and set the primary as the most expensive in Senate history.
The Record-Breaking Ad Blitz That Failed
Cornyn's side poured more than $100 million into television and digital advertising during the primary. This total made the contest the costliest Senate primary ever recorded. Most of the money came from Cornyn's campaign and allied groups rather than from Paxton's operation.
The scale of the spending produced no victory. Instead, it highlighted a misallocation of resources that left other Republican priorities underfunded. Observers noted the outlay diverted cash that could have supported candidates in tighter races elsewhere.
| Candidate Side | Primary Ad Spending | Outcome |
|---|---|---|
| John Cornyn and allies | $100 million+ (up to $128 million per AdImpact) | Lost runoff |
| Ken Paxton | Not detailed in filings | Won nomination |
Trump Endorsement and the MAGA Shift
President Trump endorsed Ken Paxton before the runoff. The endorsement aligned with Paxton's stronger appeal among Republican primary voters who favored the former attorney general's approach. Cornyn's defeat reflected the party's continued movement toward candidates backed by Trump.
Paxton's win consolidated support from the MAGA wing. Cornyn, a longtime senator, could not overcome that alignment despite the heavy advertising investment. The result underscored how endorsements from the former president now carry decisive weight in Texas Republican contests.
