US Democrat Harris gets backing from more than 100 venture capitalists

(Adds quotes from donors, paragraphs 6-9)

WASHINGTON, July 31 (Reuters) - More than 100 venture capitalists including entrepreneur Mark Cuban threw their support behind U.S. Democratic presidential candidate Kamala Harris on Wednesday, a counterweight to tech billionaires backing Republican rival Donald Trump.

Silicon Valley has traditionally been seen as a liberal bastion, but Republicans have won support from prominent industry figures in this election cycle. They were bolstered by Trump's selection of U.S. Senator JD Vance, a former venture capitalist, as running mate. But President Joe Biden's decision to drop off the Democratic ticket on July 21 has reenergized some in the tech industry who previously had stayed on the sidelines.

"We spend our days looking for, investing in and supporting entrepreneurs who are building the future. We are pro-business, pro-American dream, pro-entrepreneurship, and pro-technological progress," the group said in a public petition posted online.

"We also believe in democracy as the backbone of our nation. We believe that strong, trustworthy institutions are a feature, not a bug, and that our industry - and every other industry - would collapse without them."

Reid Hoffman, a LinkedIn founder, investor Chris Sacca, Katie Stanton of Moxxie, Eva Ho of Fika Ventures and Rebecca Kaden of Union Square Ventures, were among those who signed the letter and pledged to vote for Harris in the Nov. 5 election.

Box CEO Aaron Levie, a Democratic donor, told Reuters that many people in Silicon Valley were "disillusioned" with the state of the Democratic Party under Biden. Levie, who is not a VC, has not signed this petition but has donated to Harris' campaign, as well as Biden's before he dropped out.

Harris's ascension "completely changed the landscape," he said, pointing to a flurry of donations both public and private from his industry peers. The floodgates could open further, he said, once Harris laid out her stance on business and technology.

Zynga founder Mark Pincus, another Democrat donor who earlier this month wrote in an op-ed that Biden was riskier than Trump, said he was now "undecided and confused." Harris's demonstration of a pro-innovation platform could clear up the confusion, he told Reuters in an email.

"So far Trump and the GOP have said the right things on these fronts but who knows if we can trust him," Pincus said.

Wednesday's letter from venture capitalists comes after Trump drew support from other wealthy, high-profile Silicon Valley venture capitalists and investors.

Elon Musk, the billionaire CEO of Tesla, publicly endorsed Trump for the first time after the July 13 assassination attempt on the former U.S. president.

Entrepreneur and investor David Sacks, the former chief operating officer of PayPal and a close friend of Musk, has also hosted fundraisers for Trump. (Reporting by Doina Chiacu in Washington and Kenrick Cai in San Francisco; Editing by Deepa Babington and Daniel Wallis)