"You have this guy who's an incredibly aggressive social media user but doesn't have any other points of resonance or commonality with the people who are creating the technology," said Paul Holland, a general partner at Silicon Valley venture firm Foundation Capital and a supporter of Clinton in this election. "His demeanor and behavior are way more aligned with a sophomore in high school than a 70-year-old businessman with immense things at stake."
On Tuesday, Hewlett Packard Enterprise CEO Meg Whitman became the latest high-profile Republican to turn on Trump, calling him a "demagogue" and pledging her support for Clinton.
Hope Hicks, Trump's spokeswoman, declined to comment, as did a spokesman for Menlo Park, California-based Facebook. A Twitter representative didn't respond to a request for comment.
There are certain days when Trump seemingly lives on social media. On Tuesday, he posted more than 10 messages on each site on topics including trade deals, a rally in Virginia and a New York Post story about Clinton's supposed ties to Russia. He also sent a tweet calling Barack Obama "perhaps the worst president in the history of the United States!"
The bombastic spontaneity has gotten him in some trouble. At last week's Democratic National Convention, the Muslim parents of a U.S. Army captain killed in the Iraq War criticized Trump for his proposed Muslim ban and for having never sacrificed anything.
Trump fought back against the father, Khizr Khan, on TV and on Twitter, saying he'd been "viciously attacked." Members of his own party sided with Khan.
His Twitter addiction was highlighted in Clinton's convention speech as a warning to the American people.
"A man you can bait with a tweet is not a man we can trust with nuclear weapons," Clinton said on Thursday night in Philadelphia.
Trump's support nationwide has plunged since the end of the DNC. FiveThirtyEight.com now gives Clinton a 68 percent chance of winning, according to the site's polls-only forecast.
Clinton is no stranger to social media. She has 8.1 million Twitter followers, 5.3 million Facebook fans and an established technology operation, led by an ex-Google executive. In July 2014, the former first lady and secretary of state visited Twitter in San Francisco and Facebook in Silicon Valley, conducting question-and-answer sessions at both campuses.
Clinton's fundraising advantage at the social media companies is mirrored across the industry. Internet businesses have donated $1.5 million to her campaign and related outside groups, over 100 times more than the $13,308 they've contributed to Trump, according to the CRP.
Seven Republicans, all who were beaten by Trump in the primary, raised more from the tech sector than the nominee.