MOUNTAIN VIEW, Calif. — Senator Clinton’s failed effort to reform health care was doomed not by the substance of what she proposed, but by the decision she and President Clinton made to develop the plan in secret, Senator Obama of Illinois is arguing.

“They made one really big mistake. They took all their people and all their experts into a room and then they closed the door and they tried to design the plan in isolation from the American people,” Mr. Obama said as he brought his campaign for the Democratic presidential nomination to Google’s headquarters yesterday.

“I would do it entirely differently,” Mr. Obama said, vowing that the health care proposal he will put forward as president would be crafted and debated entirely in public. “We are going to have a big table, and everybody’s going to be invited,” the Illinois senator said. “It will be on C-SPAN. It will be streaming over the net.”

Mr. Obama said Mrs. Clinton’s health plan was felled because the secrecy created an information vacuum in which advertising from the insurance industry was able to seize control of the debate. The Illinois senator said he wouldn’t allow such an effort to go unrebutted. “If the start running ‘Harry and Louise’ ads, I’ll put out my own ads or I’ll send out something on YouTube,” he said, referring to the Web video platform that Google bought last year in a $1.65 billion deal.

Mr. Obama’s comments about the failure of the 1993 health care reforms dovetailed with one of his recent campaign themes, namely that Mrs. Clinton has a disquieting penchant for secrecy.

More than a thousand Google staffers packed the room where Mr. Obama spoke, and hundreds more watched video feeds at the Internet company’s facilities around the world. Other presidential hopefuls who have visited have also drawn large crowds, but few saw hundreds of staffers turned away for space reasons.

Mr. Obama reflected on the diverse background of the largely young audience as he talked openly about how his African heritage and his experiences living in Indonesia could make him a more effective president.

“The day I’m inaugurated not only does the country look at itself differently but the world looks at America differently,” he said. “I could say I’ve got a grandmother in a small African village without electricity or running water. So I have a little credibility that no other president could match. If I go to a Muslim leader, I can speak to them. I can say I am a Christian, but I lived in the country with the largest Muslim population in the world.”

Mr. Obama’s comments were warmly received by the so-called Googlers, especially when he referred directly to the Web company. The Illinois senator recalled visiting Google in 2004 and remarking on a video map that displayed where Google searches were originating around the world. “What struck me wasn’t the light on that globe, it was the darkness. Most of Africa, chunks of Asia, even parts of the United States, the disconnected corners of our interconnected world,” Mr. Obama said in opening remarks promising policies that would promote innovation and bringing broadband Internet access to Americans. “You and I must not settle for anything less than an America that replaces that darkness with a new light,” he said.

Mr. Obama also insisted that his calls to close the Guantanamo Bay prison, to end warrantless wiretapping, and to repudiate torture, should not lead people to view him as liberal.

“I’m accused of being you know this ‘progressive … far-out,'” he said. “I’m conservative, in the sense that I want us to get back to those values that were essential to building America.”