Washington (CNN) If Donald Trump thought he could end this week with a high note at the G20 summit, Robert Mueller's investigation certainly scuttled those plans.

Hours before Trump boarded his plane to Argentina, a bombshell landed in Trumpworld with the news Michael Cohen had pleaded guilty to lying to Congress about -- and a sign Cohen is talking Trump's business deals with Mueller -- a previously stated "red line" for Trump.

He also defended his actions on the campaign trail: "Even if he was right, it doesn't matter, because I was allowed to do whatever I wanted during the campaign."

closer to announcing their Meanwhile, the field of would-be challengers to Trump is crystallizing, with more and more Democrats inching intentions to run.