Texas Republican Ted Cruz pissed off many Republicans by refusing support for presidential nominee Donald Trump in July at the party’s national convention. Sen. John Cornyn was one of them, who is now declining to endorse fellow Texan Cruz in the 2018 Senate race,

Cornyn, the Senate majority whip, has had similar beef before with Cruz, when Lyin’ Ted refused to back Cornyn for another term two years ago.

Cruz may be in trouble against a serious challenger, such as U.S. Rep. Michael McCaul of Austin, who has been urged to take on Cruz. McCaul has not ruled out a possible run, but a Cornyn endorsement may be key to getting things going in that direction. Though Cornyn distanced himself Wednesday from efforts to ensure a Cruz challenger, telling CNN he is “not recruiting anybody.”

Cruz’s refusal to endorse Cornyn in the 2014 primary has contributed to political speculation that the Texas’ two U.S. senators have a tense relationship. Cornyn has also said it was “a mistake” for Ted Cruz to appear at the Republican National Convention with no intention of endorsing presidential nominee Donald Trump.