The Democratic Party’s rapidly fading love affair with Big Tech has broken into open acrimony in recent weeks, punctuated by a presidential debate Tuesday in which leading candidates took turns decrying the industry’s impact on the nation and workshopping ways to rein it in.

Whether the issue was antitrust enforcement or hate speech, data privacy or screen time, Democrats expressed a common goal of bringing the major technology firms to heel.

“We have a massive crisis in our democracy with the way these tech companies are being used, not just in terms of anti-competitive practices, but also to undermine our democracy,” Sen. Cory Booker (N.J.) said. “We have seen it in the ’16 election practices being used that have not been corrected now. We need regulation and reform.”

Sen. Elizabeth Warren (Mass.) — who last week bought a Facebook ad claiming, in jest, that the platform had endorsed President Trump — reiterated her call Tuesday to break up what she called “monopolists” in Silicon Valley and pressed her rivals in Tuesday’s debate to forgo donations from “the big tech executives.” Even former tech executive Andrew Yang expressed a desire to find “the best way we can fight back against big tech companies.”

The unanimity of criticism of Big Tech marked a sharp turnabout from 2008, when a then-young social media platform, Facebook, was skillfully deployed to help elect Barack Obama president. Those warm feelings are long past, damaged by Facebook’s role in spreading disinformation against Democrat Hillary Clinton during the 2016 election campaign and its refusal to act more aggressively against viral falsehoods in this election season.

The growing frustration with Facebook and its Silicon Valley peers threatens to put the industry in the crosshairs of a future Democratic White House should the party prevail in 2020. Warren’s call for the breakup of Facebook, Google and Amazon has generated backlash within the industry, most visibly when Facebook’s chief executive, Mark Zuckerberg, told employees in July that he would “go to the mat … and fight” such an effort in court.

“Facebook was a company that was incredibly popular among the public writ large, and particularly liberals, prior to 2016. It now ranks with tobacco companies, oil companies and the NRA in driving Democratic anger,” said Dan Pfeiffer, a White House communications director under Obama, whose use of Facebook in the 2008 campaign gave early hints of its power as a political organizing tool.

Facebook, Google and Twitter declined to comment on the growing Democratic disaffection with Silicon Valley. (Amazon founder and chief executive Jeff Bezos owns The Washington Post.)

Democrats’ animosity has only grown in response to Zuckerberg’s recent courtship of conservatives, including dinners and other private meetings with right-leaning pundits and lawmakers — all at a time when some of Facebook’s most visible leaders in Washington are conservatives, too.

Katie Harbath, a former Republican strategist, including for Rudolph W. Giuliani, Trump’s personal attorney, is the company’s public policy director for global elections. Facebook’s vice president for global public policy is Joel Kaplan, a veteran of the George W. Bush White House who, last year, sat two rows behind then-U.S. Appeals Court Judge Brett M. Kavanaugh as he denied allegations of sexual misconduct before Congress and battled successfully for a seat on the Supreme Court.

Over the past few months, Zuckerberg has huddled with prominent conservatives, including Tucker Carlson, the Fox News host, and Sen. Lindsay Graham (R-S.C.), who oversees tech issues as chairman of his chamber’s Judiciary Committee. The dinners, confirmed by a person familiar with the matter who spoke on the condition of anonymity because they were not authorized to speak about the private conversations, marked Facebook’s latest efforts to try to shore up support with influential political figures on the right who at times have criticized Silicon Valley for targeting Republicans unfairly.

But the meetings, first reported by Politico, sparked immediate Democratic outrage, including a campaign on Twitter to get users to quit Facebook, under the hashtag #deletefacebook. The report also drew a rare, testy response from Zuckerberg himself, who posted on his Facebook profile that he has dinners with officials on all sides of the political spectrum. “Meeting new people and hearing from a wide range of viewpoints is part of learning,” he wrote. “If you haven’t tried it, I suggest you do!”

Polls this year have found that large swaths of the American public are skeptical of leading technology companies. A Fox News poll in June asking whether Facebook had “too much power” found agreement from roughly three out of five Americans, with little variation based on race, income level, age, gender, region or party affiliation.

Distaste for major technology companies among conservatives has been obvious for years, with many Republicans — and especially Trump — bashing the industry for unproven allegations of liberal bias in moderating their platforms. They began voicing this critique forcefully ahead of the 2016 vote, leading to a summit in which top executives hosted prominent conservatives at Facebook headquarters in Menlo Park, Calif.

For Democrats, though, the shift in opinion followed the 2016 election, when Russian operatives used the platform and other social media to spread viral falsehoods, exposing major weaknesses at Facebook that domestic and foreign sources continue to exploit to this day.

“I think that these companies have accomplished something that no one else has been able to accomplish, and that is a bipartisan, bad mood, with the word ‘antitrust’ being thrown around,” said Rep. Anna G. Eshoo (D-Calif.), whose district includes part of Silicon Valley.

Just how deeply major technology companies have fallen out of favor with Democrats was evident Tuesday as 12 of the party’s presidential aspirants took the stage outside of Columbus, Ohio. That a section of the three-hour dialogue was devoted to technology was on its own a sign of the shifting views of a party that once used Facebook and Google’s YouTube video service to elevate the country’s “first social media president,” as Obama was known.

Eric Schmidt, a top Google executive, was a visible supporter of Obama, and the company’s alumni filled key roles in his White House. The industry also was a major source of money for Democrats. Donors in the communications and electronics sectors overwhelmingly backed Clinton in 2016, contributing roughly $62 million to her campaign and outside groups compared with roughly $7 million for Trump, according to data compiled by the Center for Responsive Politics.

During a town hall at Facebook’s headquarters in the spring of 2011, Obama extolled Facebook for fostering “dialogue,” creating the conditions for a “healthy democracy.” The Obama-era optimism about social media was reflected globally, with “Facebook revolutions” unfolding from the Arab Spring to Occupy Wall Street, from Tehran to Bucharest to Lower Manhattan.

No longer do Democrats cast Internet dwellers as engaged, enlightened citizens, however. Rather, in the words of Beto O’Rourke, the former congressman from Texas, they represent the “product” for social media platforms, which “abuse that public trust … at extraordinary profits.”

For Sen. Kamala D. Harris (Calif.), the problem stems from the current occupant of the Oval Office, who commands a massive online following, with more than 65 million users tracking the president’s comments — many of them attacks on real and perceived rivals — on Twitter. Harris has asked Twitter to suspend Trump’s account for violations of its policies against harassment and hateful conduct. The platform has declined to do so, but on Tuesday clarified the rare instances in which it would take action against world leaders.

Twitter also joined Facebook and Google in refusing a request by the campaign of Joe Biden, the former vice president, to stop airing an advertisement that made false claims about him and his son’s actions in Ukraine.

That refusal — in contrast with CNN’s decision not to air the ad, and NBCUniversal’s move to stop airing it — has enraged Democrats and fueled calls for more regulation of campaign speech, putting the party starkly at odds with most of Silicon Valley. Facebook officials explicitly exempt the ads and other “direct speech” by politicians from their system of fact-checking, the creation of which was a key reform after Russians and others flooded Facebook, its subsidiary Instagram and other social media platforms with disinformation in 2016.

Warren’s call on Democrats to forgo fundraising in Silicon Valley has not yet caught on. The San Francisco Bay area has been a frequent fundraising stop for Harris as well as for Biden and South Bend, Ind., Mayor Pete Buttigieg, both of whom remained quiet during the exchange during the debate on the power of Silicon Valley.

Even the candidates who don’t take contributions from Silicon Valley have still poured money into the companies based there, in the form of digital advertising. The Democratic presidential contenders have spent roughly $5 million on Facebook ads alone during a three-week period ending Oct. 5, according to data compiled by Bully Pulpit Interactive, a Democratic consultancy.

The action on the debate stage echoed complaints heard on Capitol Hill, where Democrats say Facebook, Google and other leading companies should be doing more — not just about disinformation but a range of other issues as well.

“Before 2016, Silicon Valley was seen by Democrats as unambiguously good,” said Rep. Ro Khanna (D-Calif.), whose district includes part of Silicon Valley. “Now some people in the Democratic Party and perhaps some in Silicon Valley have realized there’s too much concentration of wealth … there are issues of privacy that are unaddressed. There is a need for thoughtful regulation, there’s a need for Silicon Valley to think more broadly about job creation and opportunity."