... it is being unable to recognize or understand the truth. That part of it means that the Republican Party is constantly doing the bidding of people even more dishonest and amoral than they are, which makes them that dishonest and amoral.
A herd of elephants is only as fast as its slowest elephant--and there are a lot of slow movers in the Republican Party. But a murder-gang of adolescent elephants is as evil as the most misbehaved elephant. The entire herd is following--and is morally responsible for--the actions of its very worst members. That's the Republican Party.