John Cornyn

The Senate race in Texas was already the most expensive primary contest for the chamber since at least 2018. A runoff election only made it more expensive.

That second round of voting between Senator John Cornyn and his right-wing challenger, Ken Paxton, the state attorney general, pushed another $29 million worth of ads in front of Texans before the election on Tuesday. The total bill for the Republican primary race? About $128 million worth of ads as of Monday evening, according to the media tracking firm AdImpact.

At least $92 million of that has been spent to help Mr. Cornyn, including $22 million in the overtime period since the first round of primary voting in early March.

Mr. Cornyn has been finding that money isn’t always enough.

The state’s senior senator, he was long the preferred choice of Senate Republican leaders and major party donors, who threw cash at his re-election effort as he struggled to prevail in a fierce battle with Mr. Paxton.

Then, after months of teasing an endorsement, President Trump backed Mr. Paxton last week, leaving Mr. Cornyn’s supporters worried that all of the money and effort would be for naught.

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