Michael Grebe, president of the Milwaukee-based Bradley Foundation, one of the nation’s most prominent conservative groups, said Friday that he would not be attending the Republican convention in Cleveland, citing Donald Trump as the reason. It was the latest sign of continuing bad blood between the candidate and the broader conservative movement.

“I declined to go to Cleveland and I gave up my delegate slot because I do not want to be part of a process which results in the nomination of Donald Trump,” Grebe wrote in an email to the Milwaukee Journal Sentinel.