The tight Texas Republican U.S. Senate runoff between incumbent Sen. John Cornyn and Attorney General Ken Paxton has kept trader focus on base mobilization and late voter shifts ahead of the May 26 vote. Polling among likely Republican runoff participants shows Paxton holding a narrow lead, reflecting stronger support from conservative and Trump-aligned voters, while Cornyn maintains advantages among college-educated and suburban Republicans. Heavy negative advertising from Cornyn-aligned groups, outspending Paxton forces by more than four-to-one, has not shifted the closely divided electorate, with fewer than 10 percent still undecided. The absence of a presidential endorsement has left the contest open, allowing Paxton’s momentum from the March primary to sustain his edge in market pricing.