I'm starting to worry that the war has already been lost...
What's it going to take to change the minds of Trump supporters?
Nothing.
In their minds, nothing short of murder on live television could be enough for them to turn. The Democrats are the *literal* enemy of the United States in every sense of the word in their minds.
Perhaps, but every stage of rationalization requires a leap of logic that not every single Trump voter is guaranteed to make.
Stage 1: "This is just fake news from bitter Democrats" - This stage popped up just after the election and held until inauguration time. It was easy to get the majority of Trump voters on board with this line of thinking having just left a contentious, ugly election process, and reporting of the Russian connection was in its earliest stages.
Stage 2: "There just isn't enough evidence there. This looks like a misunderstanding at best" - This is probably the stage most Trump supporters are at the tail end of at the moment as evidence and reporting of the Russian investigation accelerates and stories within the Trump circle become self-contradictory and unreliable.
Stage 3: "This isn't that big of a deal." - Probably the stage we're entering now as Republicans try to write off what Trump Jr. did as admittedly boneheaded but ultimately benign, and try to accept his claim that they didn't get any worthwhile dirt on Clinton from the meeting anyways. This still requires a bit of a leap of logic from Stage 2, as it's clear they're attempting to hide something.
Stage 4: "People in Trump's circle may have colluded with Russia, but Trump himself is innocent. He should pardon them" - We're probably going to arrive here very soon.
Stage 5: "It's good that Trump colluded with an adversarial foreign government to take down the real crook, Crooked Hillary" - This is the final stage of rationalization and it would take somebody so personally invested in Trump to convince themselves into taking this position. Granted, that accounts for a sizable portion of Trump voters, but not literally all of them.