1) Mitt Romney also had to be pressed into releasing his income tax returns, which he really didn't want to do.
2) He made similar, but less extreme statements that anyone who pays more in taxes than legally necessary is kind of foolish and therefore unfit to lead.
3) But, and here's the big difference. He did release his tax returns, after possibly trying to push his total payments up to around 15% because he thought that the optics of paying less than that would be horrible. Whether or not there were active efforts on behalf of his accountants to do that was a kind of question hanging over the campaign.
Of course, 3 kind of called into question Romney's belief on 2 because Romney probably did pay more in taxes than he was legally required. Let's call it a possible campaign donation to himself, via the IRS. The fact that Trump isn't doing anything like that, and is pushing Romney's "2" even further is an interesting point of comparison.
Why? Romney backed away from 2, and Trump is constitutionally incapable of backing away from anything, which is why he keeps digging in on the Machado thing. Trump would never pay money that he doesn't have to pay. We've seen that in his business dealings. And of course, Trump's tax returns undoubtedly look very different from Romney's in ways that might garner negative media attention. More negative media attention.
Still, the Romney comparisons just keep being informative here.