Donald Trump endorsed Texas Attorney General Ken Paxton over incumbent Senator John Cornyn in their Republican primary runoff, breaking ranks with party leadership just one week before voters decide the race.

Trump's late-stage backing gives Paxton a boost from the former president's base of Texas Republicans. Cornyn, a three-term senator and former state attorney general, has held the seat since 2002 and counts backing from the state's Republican establishment and national GOP leaders.

The endorsement exposes fractures within the Republican Party ahead of a consequential runoff. Cornyn positioned himself as a steady institutionalist while negotiating bipartisan deals on border security and gun policy in the Senate. Paxton built his profile fighting federal government overreach, positioning himself as a Trump-aligned conservative who challenges the Senate's traditional approach.

Paxton faces serious legal jeopardy. The FBI and Department of Justice have investigated him on federal bribery and corruption charges related to his office's handling of cases. Texas state lawmakers attempted to remove him through impeachment, though the state Senate acquitted him in 2023. These legal clouds have shadowed his campaign, yet he maintained strong support among Trump-aligned primary voters.

Trump's endorsement signals his continued grip over Republican primary politics, even as he faces multiple criminal indictments nationally. The endorsement contradicts efforts by national Republican leaders to maintain party unity and protect Senate seats in a cycle where Republicans need gains to retake the chamber from Democrats.

Cornyn has emphasized his legislative accomplishments and relationships in Washington. Paxton's campaign centered on conservative grievances and alignment with Trump's populist messaging.

The runoff winner advances as the favorite in the general election, given Texas's Republican lean. Trump's intervention adds unpredictability to a race that could reshape the Texas delegation and signal how the former president plans to wield his influence in future