Can you use the availability heuristic against yourself?
It surely must be that repeating lies over and over convinces the liar. I've experienced several people in my life, including one parent who I won't identify except to say it wasn't my father, tell the most outrageous fabrications and be adamant that they were the truth.
Maybe it's like waiting for the bus: the longer you wait, the more you've invested in the conviction that the bus will come and you'll lose face if you just start to walk. Once you've told the lie, and so much of your sense of belonging and identity are caught up in that lie, you're stuck. Or as my Great Aunt Lucille used to say, 'Oh, what a tangled web we weave when first we practice to deceive.'
Maybe telling these lies is a way to "get at the Liberals" and that end justifies anything.
Maybe if you actually believe the bullshit you're repeating, it's not a lie. The actual lie, the actus reus, is present, but the mens rea of lying isn't.
Or maybe these Republicans are just plain amoral and evil.