I wouldn't say republicans as a general group is dishonest. I think there is an aspect of the Trump-phenomena which is dishonest in two ways: Firstly, overtly dishonest (but this is rare and mostly found in its leaders) by saying things known not to stand up to facts but secondly (and I think this is more common) accepting or excusing dishonesty.
The main reason for accepting dishonesty such as for instance, that Trump promises more healthcare and then delivers a plan which offers less, or promises he has a plan to eradicate ISIS and then does not have a plan, is because Trump supporters in my experience are not driven by a positive vision for the US/world, but rather driven by fear and negativity aimed against certain targets like Hillary, Obama, Muslims, Jews (though most commonly only acceptable Jewish targets, like Soros) or global trade.
Once you are basing your perception of the world on how evil some people are, excusing errors from your own side as "the lesser evil" becomes second nature. That is why any discussion of Trumps flaws is immediately diverted into a discussion of the acceptable targets, and why the evils of the acceptable targets must now be magnified in proportion to how bad poor Trumps performance is to cope with the cognitive dissonance.
And so as more is revealed about Trumps connection with Russia, Obama must be made more evil by the invention of a false wiretapping story which his supporters immediately accept because of cognitive dissonance.
