Mason Harrison, Crowdpac's head of communications, explained the gap. "Donors give to support candidates they love, not to defeat candidates they fear," he said.
A few billionaires are taking the opposite approach, acting instead of talking. Dustin Moskovitz, a founder of Facebook, said he was giving $20 million to various Democratic election efforts, the first time he and his wife, Cari Tuna, have endorsed a candidate. He declined to be interviewed.
Part of the problem for Mrs. Clinton is that, however preferable she may be to Mr. Trump in the tech community, she pales in comparison to President Obama. After some initial misgivings, Silicon Valley found their champion in him. There has been a revolving door between tech and the Obama administration, just as previous Democratic administrations had a revolving door with Wall Street. In June, President Obama seemed to suggest that he might become a venture capitalist after his term ends.
Mrs. Clinton is not as enthusiastic toward Silicon Valley and its disruptive ways. In a speech in the summer of 2015, she noted that start-ups in the "on-demand or so-called gig economy" — Uber, Airbnb and their ilk — were "unleashing innovation" but also "raising hard questions about workplace protection and what a good job will look like in the future."
The Clinton campaign declined to comment. The Trump campaign did not respond to a query.
Even as Silicon Valley works against Mr. Trump, there is quiet acknowledgment that his campaign has bared some important issues. In an endorsement this month of Mrs. Clinton, the venture capital firm Union Square Ventures pointed out that "the benefits of technology and globalization have not been evenly distributed," and that this needed to change.
If Silicon Valley's political involvement outlasts this unusual election, the tech community may start contributing more to the process than commentary and cash.
"Not only are tech people going to be wielding influence, but they're going to be the candidate," said Mr. McClure. "Reid Hoffman, Sheryl Sandberg" — the chief operating officer of Facebook — "and a bunch of other folks here have political aspirations."
Others may be inspired to enter politics through other doors. Palmer Luckey is the 24-year-old founder of the Oculus virtual reality company, which he sold to Facebook for $2 billion. Mr. Luckey donated $10,000 to a group dedicated to spreading over-the-top messages about Mrs. Clinton both online and off. The group's first billboard, said to be outside Pittsburgh, labeled her "Too Big to Jail."
Mr. Luckey told The Daily Beast that his thinking "went along the lines of, 'Hey, I have a bunch of money. I would love to see more of this stuff.'" He added, "I thought it sounded like a real jolly good time." Many virtual reality developers were less happy, and Mr. Luckey quickly posted his regrets on Facebook. He declined to comment further.
"If we're going to be more vocal, we'll have to live more transparently," said Hunter Walk, a venture capitalist whose campaign to persuade tech companies to give workers Election Day off signed up nearly 300 firms, including Spotify, SurveyMonkey and TaskRabbit. "There will be a period of adjustment."
But perhaps being vocal is a temporary condition after all. The venture firm CRV was in the spotlight at the end of August with its blunt anti-Trump message, which included the earthy epithet. A few weeks later, it cleaned up its website. The partners went from employing a publicist, to seek out attention, to declining interviews.
"We reached everyone we wanted to reach, and hopefully influenced opinions," said Saar Gur, a CRV venture capitalist. "Then the buzz died down and we went back to our day jobs, which are super busy."