As the US gears up for its next general election, half of Americans view fake news as a bigger threat to the country than terrorism, illegal immigration, violent crime or racism, according to a new study.

The 2016 presidential race was widely regarded as a wake-up call to the spectre of foreign influence, following what the US government concluded was a “systematic” Russian campaign to undermine its democratic process. But under the Trump presidency, fake news and misinformation has also grown into a new front in US political warfare.

The result, according to the study by the Pew Research Center, is that almost 70% of Americans feel fake news and misinformation have greatly affected their confidence in government institutions, and experts warn of a deepening crisis if the status quo is left unchecked.

“I think we will rue the day when we don’t step up,” Mark Warner, the top Democrat on the Senate intelligence committee, told the Guardian in an interview. “The platform companies – Facebook, Twitter, Google – are alert to the fact that there’s a problem, and they have taken firm actions of self-policing.”

“But from a guardrails or rules-of-the-road standpoint, remarkably we’ve done nothing.”

A host of top 2020 Democratic presidential contenders have recently been the targets of content that, despite being false, has been widely shared across social media. A doctored video of the House speaker, Nancy Pelosi, misleadingly edited to suggest her speech was impaired or was perhaps drunk, was disseminated by Donald Trump and ratcheted up millions of views on Facebook before the company belatedly took action to demote, but not remove it.

“The impact of made-up news goes beyond exposure to it and confusion about what is factual,” said Amy Mitchell, the group’s director of journalism research. “Americans see it influencing the core functions of our democratic system.”

The proliferation of the Pelosi videos and other falsified political content reminds us of the 2016 cycle, when rightwing conspiracy theories about Democratic presidential nominee Hillary Clinton’s health and mental fitness were amplified by doctored content online. Russian-led efforts to swing the election in Trump’s favor made use of fake advertising and videos to sow discord in the US by seizing on divisive issues that included race relations, immigration and gun rights.

Special counsel Robert Mueller’s 448-page thoroughly detailed how the Russians set up fake social media accounts to spread misinformation that reached “tens of millions of US persons”.

But despite hauling executives at tech giants Google, Facebook and Twitter to Capitol Hill to testify before Congress on a handful of occasions, lawmakers in Washington have yet to take concrete action.

Facebook was criticized for being slow to respond to the altered Pelosi videos, and some questioned if it was effective to simply demote the content and make it more difficult to find.

Meanwhile several Democratic presidential contenders have had to weather their own headlines in a fake news cycle: A fake image purported to show a blackface doll on Senator Elizabeth Warren’s desk; a series of sensationalized stories circulated about Kamala Harris’s relationship with a former male colleague; and the South Bend mayor, Pete Buttigieg, was falsely accused of sexual misconduct in a story that amounted to a hoax. And we are still 18 months away from the actual election.

Facebook’s CEO, Mark Zuckerberg, testifies before Congress in 2018. Photograph: Aaron Bernstein/Reuters

Sarah Miller, the deputy director of Open Markets, said it was insufficient to expect social media companies to self-regulate in an environment where their businesses were based on surveillance and data mining.

“It’s the fundamental business model of Facebook and Google to promote content that is sensationalistic and engaging, whether or not it is responsible content,” she said.

Miller said federal lawmakers must push for breaking up Facebook and reversing its acquisitions of other popular social networking apps Whatsaspp and Instagram.

“Since Facebook has monopoly status in the market, users have no power to drive market-based accountability,” she said. “If government doesn’t step in, then I don’t see anything fundamentally changing.”

“It’s a systemic issue,” Miller added, “and Congress has the authority to change it.”

Warner said there was bipartisan agreement that the social media platforms must be reined in, but he acknowledged a lack of consensus on how far to go.

Warner, who is working on legislation to address these issues, said solutions could range from regulating digital campaign advertisements by online companies such as Facebook and Google, identity validation and geo-locators to more clearly distinguish between bots and real people, and increased transparency around how consumer data is used by social media platforms.

“I don’t think anybody’s fully figured this out. I think the platforms have been very slow to react,” said Warner, while adding the Pelosi video underscored the complexity of identifying outright fake content versus altered material.

“If you simply put a thumbs down or a small icon that indicates this is fake, and you can cut out the icon and still deliver it on a wide basis, the bad guys are going to be successful,” he said.

As the US mulls a commensurate response, its counterparts in Europe have paved the way for enforcing privacy rights and better protecting consumer data through the implementation of policies such as GDPR. The European commission has also issued a warning to Facebook, Google and Twitter to amplify its tactics to fight fake news or risk being hit with more heavy-handed regulations.

Recent data shows that more than half of internet traffic comes from bots, and that the misinformation epidemic has expanded to fake polling, fake fundraisers and fake thinktanks.

Last week, Facebook said it had removed a record 2.2 billion fake accounts in its first quarter of 2019. Although the company did not attribute the fake accounts to a specific country, group or entity, Guy Rosen, Facebook’s vice-president of integrity, said: “The larger quantities of fake accounts are driven by spammers who are constantly trying to evade our systems.”