AUSTIN, Texas — What could have been a tight, tea party-fueled primary now looks like a cakewalk for U.S. Sen. John Cornyn after his challenger ran a campaign so disastrous that even top grassroots activists in Texas have disavowed him.

Cornyn, the Senate’s No. 2 Republican as minority whip, should have little trouble securing the GOP nomination Tuesday in his bid for a third term, even though some activists dismiss him as too moderate and his firebrand colleague, U.S. Sen. Ted Cruz, has refused to say whether he’ll vote for him.