WASHINGTON — Nearly 40 states filed a wide-ranging antitrust lawsuit against Google on Thursday, saying the tech giant manipulates its search results to give its own products and services greater rankings over rivals, depriving web users from seeing the best options whenever they query the Web for shopping, dining, travel and more.

The lawsuit by the state attorneys general, including Maine’s, marks the third competition case that U.S. regulators have filed against the search-and-advertising giant since October, reflecting the rising unease with Google’s massive profits and expansive reach and the growing national dissatisfaction with Silicon Valley writ large.

In the latest legal salvo, Democratic and Republican attorneys general from states including Colorado and Nebraska take aim at a broad swath of Google’s digital empire. They say Google has solidified its monopoly in search through an array of anti-competitive tactics, such as special deals to ensure that it is the default option on Web browsers, smartphones and newer connected devices, such as smart televisions and speakers.

State investigators also criticized Google for the way it presents its search results, which often requires companies to purchase ads if they want to rise to the top of users’ pages. In doing so, Google is able to drive adoption of its own advertising products and services, enriching its bottom line and further entrenching its dominance.

Google did not immediately respond to a request for comment.

Google for years dodged U.S. antitrust scrutiny. Nearly a decade ago, federal watchdogs similarly probed Google out of concern that it had been acting anti-competitively; a government agency concluded its inquiry in 2013 without bringing a case against the company and its sprawling search business. The U.S. ultimately stood alone in opting against seeking massive penalties against Google, even as European regulators issued a battery of punishments – and roughly $9 billion in fines – over allegations that the tech giant acted anti-competitively.

Now, though, Google faces a political and regulatory assault aimed at the very heart of its business. On Wednesday, Texas Attorney General Ken Paxton led nine fellow Republican officials in suing Google over its advertising practices, saying the tech giant illegally sought to suppress competition and reap massive profits from targeted advertisements placed across the Web.

Less than two months earlier, the Department of Justice filed an antitrust case. The complaint took aim at Google’s special arrangements to ensure that its search engine is set as the default option on an array of devices, including Apple’s iPhone, and services, such as the Mozilla Firefox browser. Google denies the charges that its practices violate federal competition laws.

Much like the earlier state and federal lawsuits, Colorado, Nebraska and other states on Thursday say Google’s unlawful conduct allowed it to become the most widely used search engine in the United States. Google says it earned its market dominance through highly lucrative targeted advertisements cued to users’ browsing behavior.

“Google sits at the crossroads of so many areas of our digital economy and has used its dominance to illegally squash competitors, monitor nearly every aspect of our digital lives, and profit to the tune of billions,” said Letitia James, the Democratic attorney general of New York, one of the eight state leaders driving the Google case.

The antitrust lawsuits against Google have coincided with a broader regulatory reckoning across Silicon Valley. State and federal officials announced last week two wide-ranging antitrust lawsuits against Facebook, saying the social-networking giant sought to buy, bully or kill its rivals, harming competition and leaving users with few other options online. The lawsuits called on a federal judge to consider breaking up the company, setting up a confrontation between the U.S. government and one of Silicon Valley’s most powerful firms.

Federal regulators – and lawmakers on Capitol Hill – also have probed Apple and Amazon over competition concerns. And some federal policymakers have sought broad revisions to federal antitrust law, hoping to make it easier to prosecute competition abuses in the future. Amazon CEO Jeff Bezos owns The Washington Post.