Google dominates Internet searches, online advertising and now mobile devices. But one of the biggest threats to the tech juggernaut these days isn’t another competitor. It’s Washington.

Enter Eric Schmidt, Google’s former chief executive and the man tasked Wednesday with reassuring lawmakers on the Senate Judiciary antitrust subcommittee that the search company is not illegally abusing its power, even as government antitrust officials have begun investigating the firm.

Getting grilled on Capitol Hill has become a rite of passage for many big companies that draw scrutiny. The moment is a very public test for Google, which has largely worked behind the scenes in recent years to build up its presence in Washington.

This will be Schmidt’s first time testifying on the Hill, but in many ways, Schmidt, a Washington native, is hardly a political neophyte. He hit the campaign trail in 2008 to support Barack Obama’s run for president, and he helped with the administration’s transition into office. Schmidt sits on Obama’s Council of Advisers on Science and Technology, and he chairs the board of a prominent Washington think tank, the New America Foundation.

In recent weeks, Schmidt has made three visits to Capitol Hill to talk with members of the Judiciary Committee, said Google spokesman Adam Kovacevich.

But Schmidt will be under pressure by lawmakers to explain why Google isn’t violating the country’s antitrust laws.

The broad antitrust argument against Google goes like this: The company’s dominant share of the search market means that it has unparalleled influence over what users find and don’t find on the Internet. As Google has branched into products beyond its main search engine, including mapping, travel and shopping, companies have accused Google of giving its own content better placement in its search results. Critics say this hurts not only smaller companies but also consumers, who don’t get the best results.

Google says that users are free to use other search engines and that when the company places its own results higher than others, it’s merely trying to give users the information they want faster.

“We’re moving from the standard 10-link answer to being able to give you an answer,” Schmidt said in an interview with Christiane Amanpour on ABC’s “This Week.” “We found that what people want when they go to Google is that they want the answer right now.”

But Google’s competitors worry that users will miss them entirely if they don’t show up high enough on search results pages.

“If Google’s goal is supposedly to get users to where they [want to] go as quickly as possible, why are they pushing entire categories of successful popular sites to the bottom or off the page?” said Tom Barnett, counsel to travel search site Expedia and former assistant attorney general in charge of the antitrust division of the Justice Department. Barnett is scheduled to testify Wednesday.

Both the Federal Trade Commission and the European Union have begun inquiries into Google’s practices.

Some members of the Senate Judiciary Committee have expressed concerns about Google’s dominance, but the power to impose restrictions on the company’s behavior lies with antitrust officials.

Other witnesses Wednesday will include Jeff Katz, chief executive of shopping comparison site Nextag; Jeremy Stoppelman, co-founder and chief executive of user review site Yelp; and Susan A. Creighton, counsel for Google.

“I’m pretty comfortable we’re in good shape,” Schmidt said during the ABC interview.