What did Donald Trump do today?

He admitted he'd lied to the American people about his business interests in Russia.

This morning, Michael Cohen, Trump's fixer and longtime Trump Organization executive, pleaded guilty to lying to Congress. Cohen admitted that he'd lied to protect Trump politically, by (falsely) saying that Trump wasn't seeking to do business in Russia during the campaign.

Since entering politics, Trump has insisted over and over again that he had no business interests in Russia.

Reacting to the Cohen plea, Trump was forced to admit this afternoon that he'd been pursuing a massive construction project in Moscow well into 2016, and that, notwithstanding his years of denials, that "everybody knew about it."

Specifically, as BuzzFeed News reported today, Trump was dealing directly with Dmitry Peskov, a Putin lieutenant. Trump wanted to give Putin a $50 million penthouse in the proposed Moscow Trump Tower, in the hopes of making the money back from other Russian oligarchs.

Voters knew none of this. Almost all of the 2016 Republican primaries had taken place by the time work finally stopped on the project. That fact raises national security concerns. By engaging in secret deals with Russian interests, and deliberately concealing them from voters, Trump gave the Putin regime leverage over him.

This may to some extent explain Trump's astonishing deference to Putin, even after he became president. And that in turn would explain Putin's willingness to go extraordinary lengths to make sure that Trump became president.

Why should I care about this?

• It's bad if a presidential candidate hands a hostile foreign power the tools to blackmail him with.

• It's wrong to lie to voters about things that would make them not vote for you if they knew the truth.

• The part where Trump tried to give Vladimir Putin a $50 million gift.