The state attorneys general from four dozen states officially declared on Monday that they were beginning investigations into the market power and corporate behavior of big tech companies.
The formal declaration, delivered from the steps of the United States Supreme Court by a bipartisan group of state officials, adds investigative muscle and political momentum to the intensifying scrutiny of the tech giants by federal watchdog agencies and Congress.
The states are focusing on two targets: Facebook and Google.
Letitia James, the Democratic attorney general of New York, announced on Friday that a bipartisan group was investigating Facebook. That came with a simple press statement. The event on Monday, formally announcing the Google investigation and discussing Facebook, was a news conference in the nation’s capital.
Ken Paxton, the Republican attorney general of Texas, another large state with a sizable legal staff, is taking a lead role in the Google inquiry.
In a statement, Mr. Paxton noted that there was nothing wrong with a company becoming big and powerful. But, he said, “we have seen evidence that Google’s business practices may have undermined consumer choice, stifled innovation, violated users’ privacy and put Google in control of the flow and dissemination of online information.”
The state inquiries coincide with bipartisan scrutiny of the tech companies in Washington, by House and Senate committees, the Justice Department and the Federal Trade Commission. Federal officials are examining the practices of Amazon and Apple as well as those of Facebook and Google.
The states can play a key role, often in concert with federal regulators and Congress, in building evidence and public support for major investigations. That was the pattern in the landmark antitrust case against Microsoft, when 20 states joined the Justice Department in suing the software giant in 1998.
The highly public declaration on Monday was partly political theater, but it was also seen as a signal of the states’ commitment.
“This kind of high-profile announcement creates expectations, and it does put pressure on the federal agencies to follow through — to seriously investigate these companies,” said Andrew I. Gavil, a law professor at Howard University. “And by making it bipartisan, they are wisely laying the groundwork for what could be a lengthy and far-reaching investigation.”
Investigations could eventually lead to the breakup of some companies, and to new laws that might alter the balance of corporate power.
The investigation into Google has been joined by 48 states as well as the attorneys general for the District of Columbia and Puerto Rico. The states that have not joined the inquiry are Alabama and California, the home to Google and Facebook, Mr. Paxton said at the news conference.
Major antitrust inquiries can take years, whether they result in legal action or not.
The states have been looking at the big tech companies amid rising concerns about their power in markets and their influence in public communication and political debate. The states formed a multistate unit called the Tech Industry Working Group months ago.
They steadily built up support, both getting bipartisan backing and enough states to marshal the legal resources to pursue in-depth investigations and potentially an antitrust suit.
Each investigation has a smaller core group of states, evenly split between Democrats and Republicans. And they are supported by a larger collection of states that agree to join the effort.
“Obviously, we’re just beginning, but this is going to be a thorough investigation,” said Phil Weiser, the Democratic attorney general of Colorado.
Colorado is a member of the core group in both the Facebook and the Google investigations, and Mr. Weiser is an antitrust expert, having served as a federal antitrust official in the Clinton and Obama administrations. “I’m not worried about having the legal and intellectual firepower for these investigations,” he said.
Unlike the Microsoft case, which focused on a single company, the concerns about today’s tech giants cover a range of markets and issues.
The various investigations reach beyond the companies’ size, wealth and market power — the usual concerns of antitrust regulators. The companies’ handling of consumer data, their ad-targeting practices and their role as gatekeepers of communication are all under scrutiny, both in the United States and in Europe.
In 2017, Josh Hawley, who was the attorney general of Missouri, began an investigation of Google. At the time, it was a lonely pursuit. He said the large, bipartisan effort announced on Monday was a sign of the times.
“This really speaks to the increased awareness and concern” surrounding the big tech companies, said Mr. Hawley, now a Republican senator from Missouri. “They’re hearing from people in their states.”