President Donald Trump's delayed endorsement in the Texas Senate Republican primary runoff between incumbent John Cornyn and challenger Ken Paxton remains the central focus for traders assessing candidate prospects ahead of early voting on May 18. Recent developments include Cornyn's May 10 repost of material from Republicans critical of Trump, which triggered immediate backlash from MAGA-aligned voices and renewed pressure on the president to clarify his stance. Trump has publicly stated he likes both candidates and expects to decide "maybe relatively soon," echoing earlier comments after the March 3 primary forced the runoff. This uncertainty, combined with Paxton's alignment on key legislative priorities such as the stalled SAVE America Act, continues to shape trader assessments of endorsement timing and recipient. Historical patterns show Trump's backing often shifts primary dynamics in competitive Republican contests.