Donald J. Trump wants you to be afraid. Very, very afraid.

That much was abundantly clear in a speech he gave on Monday, reading with faux gravitas from a teleprompter about the shooting at a gay nightclub in Orlando that killed 49 people early Sunday morning.

This is a tried-and-true political strategy.

“Whenever there’s a tragedy, everything goes up, my numbers go way up,” Mr. Trump bragged last December, after the shootings in San Bernardino, Calif.

And so Mr. Trump has continued to ratchet up the fear factor with each subsequent attack abroad or at home, always using it as proof of his own rightness. While it’s a tactic that helped him win the Republican nomination, that doesn’t mean it will work going forward.

Alan Abramowitz, a political scientist at Emory University, said that Mr. Trump’s strongman rhetoric and fear-stoking portrayals of Muslims may have worked in the Republican primary, but aren’t likely to win that many voters over to his side in November.