Trump's tweet raises obstruction of justice questions
Trump's tweet today about Michael Flynn was expected — he can't help but fire off on Twitter when he's upset about something. But he likely wasn't expecting the tweet to set off alarms about whether he obstructed justice.
Between the lines: Trump tweeted "I had to fire General Flynn because he lied to the Vice President and the FBI." This suggests Trump knew that Flynn lied to the FBI when he met with former FBI Director James Comey (after Flynn resigned) and specifically asked him to let the investigation of Flynn go.