So who emerged the winner after the three-month standoff between Microsoft and Yahoo? Maybe neither.

Instead, it was Google, their chief rival and the dominant player in Internet advertising, that appeared stronger after Microsoft’s bid to buy Yahoo unraveled over the weekend, according to analysts and the judgment of Wall Street.

The Mountain View, Calif., company already had taken a commanding lead in search advertising, the largest single chunk in the $21 billion online advertising market in America, according to the Interactive Advertising Bureau.

Microsoft, and many advertisers, had hoped that with Yahoo it might form a credible competitor to Google. But with the abandonment of the Microsoft-Yahoo negotiations on Saturday, it is unclear what strategy either has for gaining on the front-runner, leaving Google its dominant role in shaping the burgeoning Web business.

Whether any company can catch Google in the race for online advertising — and a preeminent position in shaping the economics of Web content — is a question that now absorbs many businesses in the Internet realm.

To pacify shareholders, Yahoo will probably seize any opportunities to enhance its business, analysts said. Yahoo could continue to pursue a deal with Google in which Google would provide the advertising that accompanies Yahoo’s search results. Such a deal would immediately increase Yahoo’s ad revenue.

Yahoo might also seek to acquire AOL, Time Warner’s Web unit, an analyst with Susquehanna Financial, Marianne Wolk, said. So might Microsoft. And Google, which has a 5% stake in AOL, could try to enlarge its holdings in order to block a Microsoft or Yahoo takeover, Ms. Wolk said.