I don’t think the problem in this case is one of excessively high standards. I think the problem is that our political system selects people who are good, talkers, who can spin a narrative, who can and do lie convincingly. After 50 years following politics my heuristic is to ignore what politicians say and watch only their actions. I find that what they say is generally devoid of useful information. The only conclusion one can draw is that they want you to believe what they are saying. Track record is the only useful guide to their likely future actions.
There is still difference between “X can lie convincingly” and “X lies completely transparently, but his voters don’t care”. With the former, you can try to convince his voters that he lied about something important. With the latter… you would just waste your time, they obviously don’t care.
It seems to me the latter are worse, but I cannot explain exactly why. Perhaps some intuition like “if voters forgive lies so easily, they would probably forgive other things, too”. Or maybe a feeling “if people are trying, all hope is not lost yet” (here “people” refers to the voters, not the politicians).
EDIT: Reading what I wrote here, I guess it’s not about openly lying politicians being necessarily worse, but rather about this being an evidence that there is something seriously wrong with the voter base, which is even more dangerous in long term.
There is of course a possibility that most voters do not genuinely approve of X being a liar, but still for some reason consider him a lesser evil compared to Y. Still makes me worry, because those voters may fix their cognitive dissonance in a way that will cause harm later.