What did Donald Trump do today?

He showed how worried he is about his tax returns being looked at.

Today, Trump took the highly unusual step today of asking to join, as a private citizen, his own administration's court battle with Congress over access to his tax returns. Earlier this year, House Ways and Means chair Rep. Richard Neal instructed the Treasury Department to provide that committee with copies of Trump's personal and business tax returns for the past six years. 

Legally, Congress's case against the Trump administration is extremely strong. By the plain text of the law, the IRS simply has to provide any requested returns, as long as they are viewed in a secure facility. Neal didn't even have to provide a reason—although he did anyway. 

Joining the suit as an individual doesn't really change Trump's chances of winning in the courts, although he may be hoping that it will let him keep things tied up in court until after the 2020 election. 

Ironically, Trump is one of the relatively small number of extremely wealthy Americans who appears to have genuinely broken tax laws, rather than simply taking advantage of legal tax shelters available to people with enough money and political influence. Much of Trump's inheritance, amounting to almost half a billion dollars, was funneled through tax avoidance schemes that ranged from highly questionable to outright fraud. (Even this doesn't really explain where Trump's current, post-bankruptcy fortune comes from.)

Why does this matter?

• Innocent people don't usually go to this kind of extreme lengths to conceal evidence of their innocence.

• Presidents aren't above the law.

• Ultra-rich people cheating on their taxes hurts everyone who doesn't cheat on their taxes.