Donald Trump has not broken any law. Everything we have seen is that the democrat party members are crooks.
Exactly. In firing Comey - for any reason - Trump was acting within his Constitutional powers. A President can legally fire an FBI director. It’s not obstructing justice because: there will be another FBI director, the investigation of Russia is on going in Congress, a President can express his opinion about any investigation, and because he has the power to pardon Flynn. Nothing here is independently unlawful.
Nixon conspired to commit a burglary. Clinton lied under oath. Both are acts that are independently unlawful.