Releasing tax returns isn’t required to run for president. No one has to do it. Yet, candidates have — going as far back as Nixon, actually. So for decades, presidential candidates have dutifully released their tax returns, probably without many people noticing or caring. But Donald Trump refuses to release his, and suddenly, the topic has become much more interesting. Why won’t he? No one knows, but it sure has created a lot of questions. Is he trying to hide something? And if not, then why not just release them? The official Trump campaign line is that there’s nothing for voters to learn by releasing his returns, but that’s a pathetic excuse. A lot can be hidden in a tax return, and Trump? He knows it. So Mitt Romney is calling him out on it, saying that there’s no reason for Trump to keep his tax returns secret unless he has something to hide.