That’s the question psychologist Robert Epstein has been asking in a series of experiments testing the impact of a fictitious search engine — he called it “Kadoodle” — that manipulated search rankings, giving an edge to a favored political candidate by pushing up flattering links and pushing down unflattering ones. …

Epstein, who had a public spat with Google last year, offers no evidence of actual evil acts by the company. Yet his exploration of Kadoodle — think of it as the equivalent of Evil Spock, complete with goatee — not only illuminates how search engines shape individual choices but asks whether the government should have a role in keeping this power in check.

“They have a tool far more powerful than an endorsement or a donation to affect the outcome,” Epstein said. “You have a tool for shaping government. . . . It’s a huge effect that’s basically undetectable.” …

Yet Epstein’s core finding — that a dominant search engine could alter perceptions of candidates in close elections — has substantial support. Given the wealth of information available about Internet users, a search engine could even tailor results for ­­­certain groups, based on location, age, income level, past searches, Web browsing history or other factors.