How about just putting in a flat tax without changing other elements, like adding VAT. Just set the rate accordingly.
The best thing about a flat tax is that everyone pays. Right now, there’s no skin off half of America’s teeth when new spending is introduced - as far as they’re concerned, someone else is paying for it.
The immediate change to the poor’s income can be ameliorated by charity, since higher taxed folks will now have more cash.
It might also go a long way toward helping wean the poor off some of their nastier habits.
Would you vote for a candidate who promises to raise your income taxes to a point considerably higher than they are now? If not then why should the half of the Americans who are going to see their taxes up be any different?