An array of activist groups is organizing a campaign to pressure the companies to refuse to sponsor the gathering, which many of the corporations have done for both the Republican and Democratic parties for decades.

The pressure is emerging as some businesses and trade groups are already privately debating whether to scale back their participation, according to interviews with more than a dozen lobbyists, consultants and fund-raisers directly involved in the conversations.

Apple, Google and Walmart are among the companies assessing their plans for the convention, which will be held in Cleveland from July 18 through July 21.

In addition to Mr. Trump's divisive politics, there is the possibility that protests, or even violence, will become a focus of attention at the convention. Mr. Trump has suggested that there will be "riots" if he is not chosen as the party's nominee, and the city of Cleveland recently sought bids for about 2,000 sets of riot gear for its police force.