PALM BEACH, Fla. —Everything seemed to sparkle at the Mar-a-Lago estate here on a recent afternoon. The sun glinted off the pool and the black Secret Service S.U.V.s in the circular driveway. Palm trees rustled in a warm breeze, croquet balls clicked and a security guard stood at the entrance to Donald J. Trump’s private living quarters.

“You can always tell when the king is here,” Mr. Trump’s longtime butler here, Anthony Senecal, said of the master of the house and Republican presidential candidate.

The king was returning that day to his Versailles, a 118-room snowbird’s paradise that will become a winter White House if he is elected president. Mar-a-Lago is where Mr. Trump comes to escape, entertain and luxuriate in a Mediterranean-style manse, built 90 years ago by the cereal heiress Marjorie Merriweather Post.

Few people here can anticipate Mr. Trump’s demands and desires better than Mr. Senecal, 74, who has worked at the property for nearly 60 years, and for Mr. Trump for nearly 30 of them.