WASHINGTON, June 9 -- The putting green Dwight Eisenhower had installed outside the Oval Office left golf-spike marks on the wooden floors inside. The horseshoe pit that George H.W. Bush ceremonially reopened in 1989 remained a fixture for years. The T-ball games George W. Bush hosted on the South Lawn ran for two decades. Each left something behind - a memory, a worn patch of grass, an anecdote.

What Donald Trump is leaving behind, at least for now, is a 92-foot steel arch and a wire-mesh fighting cage, and his answer when asked whether the whole structure comes down after his 80th birthday fight on June 14 was notably unhelpful. "Maybe we'll never, ever take it down," he said.

The UFC Freedom 250 event - five championship-caliber bout...