Clearly one can give various high-minded reasons why what Trump did in relation to Ukraine/Zelensky is unforgivable, under the worst interpretation, i.e. assuming Trump pressured Zelensky by withholding aid, in order to obtain a favor that would damage a domestic political opponent.
Hower, domestic support for Trump is already on pretty partisan lines.
So I'm skeptical that the latest revelation (regarding Ukraine) is going to matter much for the following reasons:
Ukraine has little diaspora in the US. If Trump did the same thing (i.e. withheld aid) to, say, Israel, it could be a different matter in terms of backlash he could expect at home.
Some of Trump's hardcore base is energised by seeing Mexicans (and other Latin Americans) deported. This is much closer to home, i.e. whatever happens in Ukraine probably seems [to them] utterly irrelevant in comparison.
Given that Trump is seen (among his base) as doing the right thing by pressuring China in all sorts of ways, it may even be seen as a positive thing that he turned the thumbscrews on some other faraway country.
That he mixed business with pleasure (to put it euphemistically) in his reasons for pressuring Ukraine may be easily forgiven among the religious right which is already quite willing to overlook Trump's personal flaws given the benefits he is seen as bringing to the movement, i.e. "modern day Cyrus" story.
So, who in Trump's base is likely to be influenced by this Ukraine affair? Are there enough "moderates" likely to tipped over by this? Is there any evidence in polling of this being possible?