Trump is different. When he is caught lying, he will often try to discredit people telling the truth, be they judges, scientists, F.B.I. or C.I.A. officials, journalists or members of Congress. Trump is trying to make truth irrelevant. It is extremely damaging to democracy, and it’s not an accident. It’s core to his political strategy.
As for Obama: His falsehoods tended to be attempts to make his own policies look better or to overstate a problem he was trying to solve. In a few cases, they seemed to be careless exaggerations he avoided repeating.