President Trump's anticipated endorsement in the Texas Republican U.S. Senate primary runoff between Attorney General Ken Paxton and incumbent Senator John Cornyn continues to shape trader assessments of likely targets. Trump has endorsed more than 130 candidates ahead of Texas runoffs and hundreds of Republicans nationwide in the 2026 cycle, yet he has withheld a choice in this contest despite stating after the March 3 primary that a decision could come relatively soon. Recent developments include Cornyn reposting material from groups critical of Trump and Paxton's alignment with efforts to advance stalled legislation, both of which could influence timing before early voting begins May 18 ahead of the May 26 runoff. The market reflects ongoing uncertainty over whether Trump will back an incumbent or a challenger in this high-profile race.