This is not very convincing. Top 1% save 40%, so they spend 60%. In order for a consumption tax to work, it would need to be in the 30-40% range. So you'd be capturing 60%*35% = 21% of income. Currently incomes tax is 27% of income for the top 1% in the US.
Add on top capital gains and you're collecting the same or more than you are now.
But that 35% sales tax is a huge increase for everyone at the bottom, that’s the point. The bottom 50% pay “no income tax”, spend roughly 100% of their income, and would have their taxes go up by XX * 35% in taxes under this scheme (where XX depends on what you put in the exemption bucket or not). There’s probably data from Washington state or similar on the distribution of purchases, but you can’t just stop at “35% would work” since you have to exempt more things if you goal is not to be regressive.
P.S. I don’t think when people call for “just sales tax” they also mean “oh and sure plus capital gains” (besides, this would just shift back towards dividends).
Add on top capital gains and you're collecting the same or more than you are now.