This demand that only persons who reveal their last five Federal tax returns may be placed on the preferential ballot for the Presidency amounts to a “bill of attainder”, a law written specifically to target one person or one very select group of persons.
No Bill of Attainder...shall be passed.
ARTICLE I, SECTION 9, CLAUSE 3, US Constitution
Yes. While written broadly enough it is clear it is meant to target Trump. And in addition to the many other reasons mentioned such a law forecloses the people the right to vote for a candidate of a tax-protest group who refuses to turn over or file tax returns as a political expression; or, to a poor person who does not need to file tax returns because he/she has little to no income.