You are right the problem is 48% pay no federal income taxes.
I would say that 80-90% of the support for higher taxes comes from this segment.
Not paying federal income taxes isn’t a problem. Some people are raising the next generation of children and shouldn’t be paying anything out of a $35,000 income. To be fair, all workers pay the SS tax and if they are self employed pay a double share. This is a regressive income tax. The lower income earners pay a higher rate than high income earners.