While it had been brewing on and off for years, the campaign by preservationists to better protect these Miami Beach homes was abruptly set in motion last month by the planned demolition of one especially notable house: a gleaming white neo-Classical house, built in 1925 by Walter DeGarmo, a prominent Miami architect of the era, that sits on the aptly named Star Island and exudes old Florida grandeur.

It does not hurt the preservationists’ cause that the house’s new owners carry splashy names in South Florida social circles. Dr. Leonard M. Hochstein, a well-known plastic surgeon, and his wife, Lisa, a Canadian model and one of the “Real Housewives of Miami,” took control of the waterfront house last year, sight unseen, in a foreclosure proceeding. They paid $7.6 million.

After sending an engineer to inspect the house, the Hochsteins decided that it was too deteriorated and outmoded to renovate. Instead, they submitted design plans to the City of Miami Beach to raze the house, as many property owners do, and build a 20,000-square-foot home, with six bedrooms, seven bathrooms, a game room and wine cellar, among other amenities. Applications of this sort are common in Miami Beach.

“That’s when the fireworks started,” Dr. Hochstein said.

When the Miami Design Preservation League, which led the movement to keep Art Deco hotels in South Beach from the rubble pile, heard about the demolition application last month, a member filed a request to designate the house at 42 Star Island Drive as historic. The designation would help protect the house, which is near the homes of Gloria Estefan and Sean Combs.

The request was unusual. Historic designation of private homes is typically sought by a homeowner who prizes the design and wants to benefit from tax deductions meant to encourage preservation. But, in this case, preservation league members felt compelled to stop the expected demolition of a “crown jewel on that chain of islands,” said Michael D. Kinerk, chairman emeritus of the league.