An anti-Trump protester holds protest sign in Cleveland. (Reuters photo)

SAN FRANCISCO: Donald Trump has promised to liven up this year's Republican National Convention. But some of America's biggest corporations are bailing on the party.Apple recently became the latest company to give the GOP's presumptive nominee the cold shoulder; it won't contribute money or products to the Republicans' big shindig in Cleveland this month.HP Inc is also withholding support, while Microsoft is giving products only, not cash. Beyond the tech industry, Ford, JPMorgan Chase and United Parcel Service have opted to withhold support.Most of these companies are also taking a pass on donating to the 2016 Democratic convention. In previous election cycles, though, several of them have given Republican organisers more sometimes far more in cash or donated products than they have the Democrats, making their pullback from the Republican gathering this year more dramatic.The reasons aren't completely clear. None of these companies publicly described its decisions as a repudiation of Trump . Several declined to discuss their thinking, while others said their sponsorship plans were decided months before Trump emerged as the front-runner for the GOP nomination.In many cases, however, their decisions became known after civil rights groups launched a public effort including billboards, letters and online messages aimed at persuading companies to withhold support for an event celebrating a candidate who's campaigned with incendiary proposals, racial rhetoric and harsh comments about immigrants and women."Of course it's because of Trump ," said Larry Sabato, a University of Virginia political scientist who has studied party conventions for more than 30 years. Business executives, he said, don't want to alienate customers who may be offended by Trump's statements. "Just as candidates don't get votes from people they insult," he said, "corporations don't get business from people they insult."Even so, Republican convention organisers say their fundraising is going well. More than 100 donors have contributed a total of US $57.5 million, or about 90 per cent of what's needed, said Emily Lauer of the Cleveland 2016 Host Committee. She declined to provide a list of sponsors. Trump's campaign did not respond to requests for comment.