Do I just take all of the causes and calculate which ones I support then the ones I don't and only pay on the ones I wish to at tax time?
To date, you have only one check-off box that wishes to know whether you're interested in spending a few bucks on the presidential election. My guess is that a lot of folks say 'no'- even though it has no effect on their taxes.
Imagine if you (or any taxpayer) had a check box for say:
$3Mill to Study Soft Shelled Turtle mating in the everglades.
$500 Big Ones to keep Hawaiian sugar farmers competitive.
$20Bill to influence voters in various state intitiatives seeking to decriminalize drug usage. Etc.
Again, just another guess, but I'm thinking a lot of 'noes'.