(Reuters) - In the run-up to the U.S. 2020 presidential election, many Democratic White House contenders have argued in favor of either breaking up or tightening regulation of companies such as Facebook Inc FB.O, Alphabet Inc's Google GOOGL.O and Amazon.com Inc AMZN.O.

FILE PHOTO: The logos of Amazon, Apple, Facebook and Google are seen in a combination photo from Reuters files. REUTERS/File Photos/File Photo

Republican President Donald Trump’s administration has also stepped up its scrutiny of Big Tech, conducting a wide-ranging probe into whether major digital tech companies engaged in anticompetitive practices.

Social media platforms are under particular scrutiny over their efforts to curb dissemination of misinformation and false claims, years after U.S. intelligence agencies said Russia used them to wage an influence operation aimed at interfering with the 2016 election. Moscow has denied the claim.

Here are the leading presidential candidates’ positions on Big Tech.

PRESIDENT TRUMP

Trump, whose digital campaign helped propel him to the White House in 2016, has stopped short of calling for tech giants to be broken up, but said “obviously there is something going on in terms of monopoly,” when asked about major tech companies in the past.

Trump’s Department of Justice announced in July it was conducting an antitrust review of “market-leading online platforms.”

Big tech companies such as Facebook, Google, Apple Inc AAPL.O and Amazon also face a slew of U.S. antitrust probes by the federal government, state attorneys general and Congress.

FORMER VICE PRESIDENT JOE BIDEN

Biden slammed big tech companies in a January interview with the New York Times, saying he had “never been a fan of Facebook” and arguing that online platforms should not be allowed immunity for content posted by users.

He also clashed with Facebook and Google over their political ad policies after they refused to take down a Trump ad that the Biden team said contained false claims about his son Hunter’s dealings with Ukraine.

Biden, who was vice president in the Silicon Valley-friendly Obama administration, has said that splitting up companies such as Facebook was “something we should take a really hard look at” but that it was “premature” to make a final judgment.

U.S. SENATOR ELIZABETH WARREN

Warren is leading the charge to break up big tech companies on the grounds they hold outsized influence and stifle competition.

She has called for legislation to restrict large tech platforms - which she would designate as “platform utilities” -from owning and participating in a marketplace at the same time. Under this law, Apple would not be allowed to both run the App Store and sell its own apps on it, for example.

The senator from Massachusetts also said she would nominate regulators to unwind anticompetitive mergers such as Facebook’s deals for WhatsApp and Instagram, and Amazon’s deal for the Whole Foods supermarket chain.

Warren has criticized Facebook’s policy of exempting politicians’ ads from fact-checking, running deliberately false ads that claimed Chief Executive Mark Zuckerberg had endorsed Trump’s re-election bid.

U.S. SENATOR BERNIE SANDERS

Sanders, who frequently criticizes corporate influence, has also called for the breakup of big tech companies such as Facebook and Amazon.

The Vermont lawmaker has also said that he will have the Federal Trade Commission (FTC) review all mergers that have taken place during the Trump administration. His broad plan to reshape corporate America would also mandate all large companies be owned partly by their workers.

Sanders has been particularly vocal in his attacks on Amazon over its tax contributions and working conditions at its warehouses.

PETE BUTTIGIEG

In general, Pete Buttigieg, who became Facebook’s 287th user shortly after it was launched in 2004 at Harvard University, where he was a student, has been more reluctant to slam the tech giants than some other candidates.

Though he has said that the breakup of big tech companies “should be on the table,” the former South Bend, Indiana, mayor does not think it is a politician’s place to designate which companies should be broken up.

U.S. SENATOR AMY KLOBUCHAR

Klobuchar has made oversight of big technology companies one of her major issues in Congress and argued for data privacy laws and net neutrality safeguards as priorities at her campaign launch in February.

She has not endorsed Warren’s plan for their breakup, saying that she would first want investigations. Her plan for her first 100 days in office includes an “aggressive retrospective review of mergers,” which she said she would pay for with an extra merger fee on “megamergers.”

MICHAEL BLOOMBERG

Former New York City Mayor Bloomberg told the Bay Area News Group in January that breaking up big tech companies “just to be nasty is not an answer” and that he does not think Senators Warren and Sanders “know what they’re talking about” on the issue. He said he was open to more limited antitrust enforcement.

The billionaire media mogul, who has launched a television and digital ad blitz, says online platforms should be legally treated the same as news publications. As the founder of Bloomberg News, he made his fortune selling financial information to Wall Street firms.

ANDREW YANG

Although Yang has said “we would be well served” if big tech companies were to break themselves up, he has argued that competition is not the answer to key problems with big tech.

Yang, the former chief executive of a start-up, has focused on the negative effects of tech on mental health and said he would create a Department of Attention Economy to look at how to responsibly design and use apps and devices.

Yang, who has benefited from a surge of grassroots social media supporters, told the New York Times in January that he did not “have confidence that any of my opponents get the internet.”

TOM STEYER

California billionaire Steyer says that monopolies either have to be dismantled or regulated, but that to win against Trump, Democrats will have to “show the American people that we don’t just know how to tax and have programs to break up companies.”

Steyer’s campaign has been noted for its massive ad spending, which helped push him to the debate stage, including more than $17 million in Facebook ads, according to Democratic digital firm Bully Pulpit Interactive.