Beyond the point that the President lies is the disturbing fact the many of his supporters still support a President who lies.
I have quickly developed a list of possible reasons.
1) - They don't perceive the lies. They evaluate the candidates on simplistic basis
2) - They are avoiding the truth by The Dunning-Kruger effect, because they lack the training of self reflection and evaluation.
3) - They like the lies better than the truth and wish to return to the child's belief in Santa Clause.
4) - Fool me once shame on you, fool me twice shame on me. He was given a temporary pass on the lies, but he need to produce on his plan.
After a little review I find 1) and 3) dismiss the intelligence of the Trump supporter, I want to believe those who fall in those cases are in a small minority. In case 2) I hope those supporters will learn and grow. In case 4) I believe evidence will quickly turn them around, this is likely why the 2018 election was a big deal for Democrats and a large loss for the Republicans.
So to answer my own question is the 2018 election, they don't believe him.