Oh, but it is, it is … traditionally, anyway. Donald Trump and George Stephanopoulos went several rounds this morning about Trump’s tax returns this morning, and to say it got contentious perhaps understates the outcome. By the time this interview ended, Stephanopoulos had raised the specter of Richard Nixon while Trump reminded ABC viewers that Stephanopoulos worked for the Clintons, a fact the ABC anchor almost never raises while conducting interviews of this type. For that, though, Stephanopoulos only has himself to blame:

ABC Breaking News | Latest News Videos

The presumptive Republican nominee Donald Trump continued to refuse to release his tax returns and today declined to reveal his tax rate.

Joining “Good Morning America” this morning, ABC News’ George Stephanopoulos asked Trump what his tax rate is, and Trump simply replied, “It’s none of your business.”

“You’ll see it when I release but I fight very hard to pay as little tax as possible,” Trump said.

The billionaire also said he has no foreign bank accounts and emphasized he runs a “clean” business.

The Clinton connection came up because Stephanopoulos cited Hillary Clinton’s release of tax returns as a contrast to Trump’s current position. Trump then immediately noted that Stephanopoulos worked for the Clintons for years before becoming an ABC television host, and that while Stephanopoulos used Hillary as a paragon of transparency, we still are working through all of the security violations created by the secret e-mail server Hillary used to avoid oversight. Trump notes that there are plenty of Hillary’s e-mails that are missing, and Stephanopoulos argues that the only e-mails missing are from Hillary’s staff — but that ignores the fact that Hillary erased more than 30,000 e-mails before finally turning over the server’s contents to the State Department and eventually the FBI. Hillary argues that these were all personal e-mails about Chelsea’s wedding plans, but that comes to more than 20 e-mails a day, every day, for the four-year period of her term as Secretary of State.

And that was data that really did belong to the public, under the Federal Records Act.

Let’s get back to the tax returns and presidential nominees, though. Are they any of our business? Four years ago, I disputed that notion, and pointed out that they generally produce nothing except cheap-shot talking points on class-warfare topics. For Trump (and for Clinton perhaps as well), that may be a different story. First, Trump has long promised to release his tax returns if he won the nomination, going back all the way to the start of his campaign, and he didn’t hedge it with conditions such as audits. By his own admission, he’s been audited for the last decade or more, so if that was really an issue, he would have mentioned it up front.

Also, Trump’s main argument for the presidency is his wealth and success. He’s going to make America great again, and we can trust him to do it because his businesses are so fabulous and successful — a point he makes again in this interview. (That was partially true for Romney too, but he also had his experience as governor and his rescue of the Salt Lake City Olympics.) If that’s the basis for his run, then Trump should share the evidence of it, especially since it has become a traditional disclosure in presidential and other races. Normally, I’d be sympathetic to the “none of your business” argument, but since Trump’s business success is the explicit reason he wants voters to support him, then it has become our business, too.