If any doubted that D's and R's are the same this should help erase those doubts. The 'establishment' is trying to protect itself from any and all outsiders.
For a reference, in the 1990's my brother was induced to run for a congressional seat in California. The district was a tight one and he thought he had a chance to win, but the party boss told him flat out they did not want him to win, they were just making a show and that seat was designated for the other party to win to maintain the 'balance' in the state.