Venture capitalist Ben Horowitz and his wife are planning to donate "a large sum" to the presidential campaign of US vice-president Kamala Harris, despite backing former president Donald Trump three months ago, according to foreign media reports. In a letter to employees from Horowitz's company Andreessen Horowitz, he emphasised the personal nature of the donation, saying he and his wife Felicia had known Harris for many years and that she had been "a good friend of both of us". The news came as a blow to Mr. Trump, whose campaign has far less cash on hand as the two candidates head into the final and most cash-burning weeks of their campaigns.