The Senate's No. 2 Republican as minority whip, Cornyn has often been named among the chamber's most conservative members, but hasn't been endorsed by Texas' junior senator, conservative firebrand Ted Cruz. Some leading grass-roots groups in Texas have also decried Cornyn as too entrenched in Washington and too cozy with the GOP establishment.
But Cornyn shrugged off those criticisms and crushed his seven challengers. It helped that the best-known, U.S. Rep. Steve Stockman, ran such a poor campaign that many top tea party leaders statewide formally disavowed him.
"As I have always suspected and tonight proves, Texans value hard work and solutions over rhetoric," Cornyn told supporters at his Austin headquarters.
Stockman conceded via Twitter less than 10 minutes after the polls had closed, then later urged his supporters to back Cornyn—though Cornyn said the pair hadn't spoken.
"I welcome that support," Cornyn said. "After this primary, it is time for Republicans ... the conservative coalition, all of us to pull together."
Famous for outlandish comments in support of gun rights and calls to impeach President Barack Obama, Stockman stunned political observers when he withdrew his re-election bid to his suburban Houston district and suddenly filed to run for Senate in December.
His campaign began with more debt than cash on hand, however, and was dogged by accusations of ethics violations—and things only got worse.
Stockman attended almost no major campaign events and even dropped completely out of sight for weeks in January, ignoring reporters and missing almost 20 votes in the House before explaining he had been part of an official overseas delegation at least part of that time.
Last week, leading conservatives suggested in an open letter to Stockman that he ran "the laziest statewide campaign to date" and added: "There is nothing about your conduct that represents the spirit of grassroots conservatives in the Texas tea party."
Casting his vote Tuesday, 66-year-old Don West, a retired landscaper in Lubbock, said he doesn't support Cornyn—but also wouldn't say whether he voted for Stockman.
"I think the tea party is going too far right but I think more liberals are going too far the other way," West said. "I'd rather go more conservative than less conservative."
Tuesday could be Cornyn's only major test, though, since none of the five little-known Democrats vying for their party's nomination captured a majority of the votes cast.
A May 27 runoff for the right to face Cornyn in November features David Alameel, a Dallas dental mogul and former top GOP donor, and Kesha Rogers, who has called for impeaching Obama and who the Democratic Party has taken the unusual step of urging voters not to support.
The Lebanon-born Alameel spent $4.5 million unsuccessfully running for Congress from Fort Worth two years ago and has promised that money won't be an object this time. He has been endorsed by Democratic gubernatorial hopeful Wendy Davis and traveled to Afghanistan in 2000 to negotiate with the Taliban about the possible handover of Osama bin Laden to U.S. authorities—but those talks stalled after the Sept. 11 attacks.
Alameel has been criticized by some fellow Democrats for giving millions of dollars over the years to both political parties—including top Republicans in Texas and nationally. Alameel says he once thought he could work with moderate Republicans, but that the party has become too extreme lately to deserve more donations from him.
"I think Democrats are alive and well in Texas," Alameel said in a phone interview late Tuesday night.
Associated Press writer Betsey Blaney in Lubbock contributed to this report.