I’m not sure that math still works. 55% of 72% of voters is only 39.6%. If non-white voters vote at the same rate as white voters, we need 40% of the other 28% non-white voters to get to 50.8%. I don’t think there’s any polling that has us that high among non-white voters, so we need a much higher turnout if we only get 55% of all whites.
The 72% includes people under 18. Since comparatively White have less children on average, the proportion of voting-age for White should be larger a little bit than that number. Then, of course, there is also the issue of turn out.