This phrase is a favorite for substituting for real-life plans and policies. He has all sorts of very pressing concerns that need immediate attention, so he says. They usually involve immigrants and especially Muslims, yet he is insistent that he is not a bigot or xenophobe. His plans are, shall we say, a bit vague and often are skipped over to get to the end result.
“I'll get rid of the bad Mexicans … in the first hour of my Presidency, they're GONE (briskly waves arm with small hand attached)!” er... Mr President Trump Sir, how are we supposed to coordinate the roundup and deportation (presumably by rocket) of the 2 MILLION or so “bad”“illegals” all within that first hour? Even Superman with the combined aid of the entire Justice League would find that unattainable, yet it is blithely assumed as a fait accompli. “Believe it.”
On how to win the war against DAESH: “I know more than the generals... Believe it!”
“The Cyber” is the next dangerous area that we will have to protect (or conquer – same same) and I'm sure he has a plan on how to accomplish that.... somewhere. “Believe it!”
All the “Believe it!”phrases cannot stand in for concrete plans and policies. He has yet to articulate anything of consequence and expects us all to “Believe it!”
I don't think the solution used by Dorothy in the Wizard of Oz by clicking the heels of my ruby slippers, or that favored by the Tooth Fairy, Easter Bunny, Santa Claus, and Single-Payer Healthcare, is suitable for use against the troubles of the world.
If I sit here amid the ashes and radioactive clouds post-Armageddon and just Believe it! hard enough....
All Will Be Well.