Voters in Texas are heading to the polls for a pivotal Republican Senate primary runoff, marking the climax of a contentious battle between incumbent Senator John Cornyn and state Attorney General Ken Paxton. The race has intensified significantly following a high-profile endorsement of Paxton by President Donald Trump, a move that has disrupted the political landscape and forced the Republican establishment to defend one of its most seasoned members.

Cornyn, a four-term incumbent and former Senate Republican Whip, initially led the field in the March primary but fell short of the threshold required to avoid a runoff. His campaign has centered on his extensive legislative experience and his ability to serve as a formidable candidate against Democratic challenger James Talarico in the upcoming general election. Conversely, Paxton has campaigned on an anti-establishment platform, positioning himself as a loyal ally to the President and a fighter against the Washington status quo, despite facing a series of well-documented legal and ethical challenges throughout his tenure as Attorney General.

The contest has become one of the most expensive and closely watched races of the 2026 cycle. While Cornyn has worked to repair his relationship with the President, Trump’s public support for Paxton has energized the challenger’s base. Recent polling suggests Paxton holds a notable lead heading into Election Day, reflecting a broader trend of the President actively seeking to reshape the GOP by backing challengers against established incumbents. As the results come in, the outcome will not only determine the Republican nominee for the Texas Senate seat but also signal the current influence of presidential endorsements within the party.