What did Donald Trump do today?

He got in legal trouble over his apparent payment of hush money to a porn actress.

As this site discussed yesterday, porn actress Stormy Daniels told In Touch magazine in 2011 in explicit and unflattering detail about her 2006 sexual encounter with Trump, which took place shortly after his wife Melania had given birth to Trump's youngest son. The Wall Street Journal discovered last week that Trump's lawyer, Michael Cohen, had created a Delaware corporation to make a payment of $130,000 to Daniels just before the 2016 election. While Cohen has denied that any sexual affair took place between Trump and Daniels, neither he nor the White House has offered any explanation for the payment.

Today, the political watchdog group Common Cause filed a complaint against the Trump campaign for accepting, and failing to disclose, an illegal and unreported in-kind contribution from Cohen's corporation. If the money ultimately came from Trump himself, he nevertheless violated reporting laws by failing to disclose it.

While hush money paid to cover an extramarital affair might seem like an odd thing for the Federal Election Commission to be concerned with, the law is quite clear that anything of value given to a campaign must be disclosed, and so must the campaign's expenditures. Former Democratic presidential candidate John Edwards was indicted in 2011 for his own sex scandal hush-money payments.

This is not the first time that the Trump campaign has run afoul of campaign finance reforms in unusual ways. By actively trying to get the "dirt" on Hillary Clinton that Russian agents dangled in front of him, Donald Trump Jr. likely broke the law against soliciting campaign contributions from foreign nationals.

Why does this matter?

• It's bad if a presidential candidate breaks the law in an effort to get elected.

• A president who had a reasonable, non-incriminating explanation for a mysterious six-figure payment to a porn star would have given it by now.