The Trump administration on Tuesday said it would explore regulating Google — an effort that would challenge protections around free speech online — in response to the president's allegations that the tech giant manipulates its search results to prominently display negative stories about him and other Republicans. President Donald Trump in a pre-dawn tweet claimed that search returns for "Trump News" were "RIGGED for me & others, so that almost all stories & news is BAD," apparently responding to a report from Fox News. Then, his top economic adviser, Larry Kudlow, said the White House is now "taking a look" at whether, and how, Google should be regulated by the government.

In the United States, regulating search results could violate the First Amendment, said lawmakers from both parties, free-speech advocates and tech experts. The Trump administration's threat drew rebukes from Democrats and even a few Republicans, who said government shouldn't play a role in monitoring search results or other content online.

"We can all agree on one thing: Poison is being spread on the Internet, but what is poison? Somebody is going to have to step in and be a neutral arbiter of what can go on, and what can't," said Sen. John Neely Kennedy, R-La., who cautioned he hadn't seen the president's tweet. "I don't want to see the government do that."

Google denied the allegations and said its search results aren't politically biased.

Trump's comments marked a major escalation in allegations of anti-conservative censorship against Google, Facebook and Twitter, which some in the tech industry worry could undermine the public's trust in the web as a marketplace of ideas.

"Google and Twitter and Facebook, they're really treading on very, very troubled territory. And they have to be careful," the president said later Tuesday. "It's not fair to large portions of the population."

Google processes 90 percent of searches globally, and its powerful algorithms return results based on their calculated relevance, a process Google portrays as neutral. Google takes into account multiple signals including a user's geographic location and browsing history, which is why Trump's search results look different from what another user might see. Social media differs from search because information on social media platforms is circulated through friends and brands that users choose to follow.

Riva Sciuto, a spokeswoman for Google, said when users "type queries into the Google Search bar, our goal is to make sure they receive the most relevant answers in a matter of seconds. Search is not used to set a political agenda, and we don't bias our results toward any political ideology."

But Google's algorithm is shrouded in secrecy, and in the past, Google has faced investigations for giving preference to its own products and services in search results. In China, Google even has explored launching a new, special search engine that would meet the demands of the country's strict Internet censors.

The controversy Tuesday also illustrates the tricky political terrain that Google and its tech peers now navigate. Regulators and users increasingly demand that Silicon Valley apply a heavier hand in moderating content that appears online to prevent harassment, stop hate speech and ensure civil political discourse. At the same time, those decisions about what to allow, and what to take down, aren't always obvious — and can create controversy. A decision this month from Facebook, Google-owned YouTube and Twitter to discipline Infowars, a conspiracy theory site founded by Alex Jones, drew the attention of the president's son, Donald Trump Jr., who tweeted that sites like Breitbart and Daily Caller could be next.

Donald Trump President thinks Google's search engine is "rigged." By featuring more mainstream news outlets and relatively fewer conservative sites in the results he sees, Trump tweeted Tuesday, Google is "suppressing" right-wing views on its platform. Trump escalated his attacks Tuesday afternoon...

Facebook declined to comment. Twitter pointed to previous statements calling allegations of systemic bias "unfounded and false."

Trump's tweets came the morning after Fox Business host Lou Dobbs aired an interview with the pro-Trump commentators Lynnette Hardaway and Rochelle Richardson, popularly known as Diamond and Silk. The duo has long said that their online videos are being suppressed by tech companies, though some of their claims have been debunked.

"I am not for big government, but I really do believe that the government should step in and really check this out," Hardaway told Dobbs in the interview.

In the past, federal courts have found that search engine results are protected speech because they resemble the editorial content produced by more traditional sources of information, such as newspapers and books.

"There's no question about this. The courts have uniformly ruled that search results are protected speech," said Eric Goldman, co-director of the High Tech Law Institute at Santa Clara University.

Sen. Brian Schatz, the top Democrat on one of the Senate's tech-focused subcommittees, lambasted Trump's tweet and threat to regulate as a "crazy, authoritarian idea," saying it is "unconstitutional, unworkable and antithetical to everything our country stands for."

Among conservatives, suspicions of bias run deep, fueled in part by high-profile mishaps at many major tech companies. In 2016, anonymous former Facebook employees suggested that the site often passed over conservative media outlets when choosing stories to curate for its "trending" news feature. Twitter has long denied charges that it limits the reach of tweets from its conservative users but doesn't tell them, a practice known as shadow-banning.

Under public pressure from Republicans, tech companies have been quick to apologize for the mishaps. Some, like Facebook CEO Mark Zuckerberg and Twitter CEO Jack Dorsey, have admitted that their companies, located in the liberal-leaning San Francisco Bay Area, have a leftward political tilt.

But that's hardly dissuaded some Republicans on Capitol Hill, where GOP lawmakers this year have already held two hearings focused on allegations of conservative bias. A key House committee intends to grill Dorsey about claims of censorship at a hearing scheduled for next week.

"They've been bluegdoning these CEOs to the point where they're now overcorrecting for perceived liberal bias," Schatz said. "I think we should understand this is a specific strategy to try to influence the way these platforms present information."

Conservatives' attacks have intensified as the 2018 election has drawn closer. Trump has tweeted three times since late July about "discriminatory" practices at Twitter and social media sites more broadly. His tweets Tuesday doubled as a new way to appeal to his supporters: Hours after he sent them, Trump's campaign cited his attack on Google in a text message asking voters to donate ahead of a key fundraising deadline. At least one lawmaker, House Republican Leader Kevin McCarthy, has purchased fundraising ads on Facebook that call attention to anti-conservative censorship online. A spokesman for McCarthy did not immediately respond to a request for comment.