The Left will say nasty things about Trump whether he releases the tax returns or not. But with them in the public domain at least he can point to a piece of hard evidence (the tax returns) to refute the Left’s claims. Having some evidence in your favor is better than having none.
Perhaps, but in context of the “impeachment” hearings, the left will take anything and RINO’s would jump on-board with dems and say; “See? See? I told you he did X-Y-Z. . .”