Stephen Ross, chairman and founder of real estate development company The Related Cos., which owns Equinox and SoulCycle, is throwing the Trump fundraiser on Friday at Ross' house in the Hamptons. Ross also owns the Miami Dolphins football team.
"Just contacted @Equinox to cancel my membership after many years," tweeted comedian Bill Eichner, who voiced Timon in the latest version of "The Lion King" movie. "If it's too inconvenient for u to trade one LUXURY GYM for another, then you should be ashamed."
Equinox and SoulCycle tried to separate themselves from Ross and his fundraiser.
"We want to let you know that Equinox and SoulCycle have nothing to do with the event and do not support it," the gym operator said on Twitter . "We believe in tolerance and equality, and will always stay true to those values. Mr. Ross is a passive investor and is not involved in the management of either business."
Other brands, such as Nike, have been the target of boycotts in the past, with little effect.
"They usually don't do much," said Laura Ries, a brand strategist and president of Ries & Ries in Atlanta. "In the age of Twitter and Instagram, these boycotts blow hot for a day or two and sputter out very quickly."
While some members may not show up for their cycling class at first, or cancel their $300 a month Equinox membership altogether, Ries said Ross is not well-known enough and doesn't have a close connection with the brands. Ultimately, she said, it won't be enough to hurt Equinox or SoulCycle.
"Tomorrow there's going to be something else," she said. "Unfortunately, people forget."
Related, which has real estate developments nationwide, bought Equinox 13 years ago. Equinox later bought SoulCycle. Together, they run about 200 gyms and studios in big cities such as New York, London and San Francisco.
Related and Equinox did not respond to requests for comment.
Mika Brzezinski, who hosts MSNBC's morning show "Morning Joe," tweeted Thursday that she would stay away from the fitness studios.
"No more soul cycle. Will never go there again," she tweeted. "Ever."