1974 Michigan Proposal C

[Oldiesfreak1854]

I just uploaded the results of Michigan's Proposal C in 1974, which removed the state sales tax on food and prescription drugs.  One of the things I noticed is that the more conservative/Republican leaning counties opposed it.  I wonder why they would have opposed an anti-tax measure like this.  Anybody have any guesses?

For reference, here's the map:

[Oldiesfreak1854]

Sales tax is a flat tax which effects the poor more. Conservatives love flat taxes.

I doubt that's why.  But I can understand why they would be worried about a graduated tax, since those are more harmful to business.
Of course, I'm conservative, and while I believe in low taxes for all income levels, I don't think I'd support a flat tax.