Former House Speaker Newt Gingrich on Sunday said Donald Trump is beginning to understand the magnitude of the presidency, comparing him to a dog that caught a bus — except, he said, in this case, it’s a convoy.“I think that particularly when he went to the White House and was in the Oval Office, he was beginning to realize that under our system, the full weight, for example, of national security is on one shoulder,” Gingrich explained on “Face the Nation” on CBS.