SAN FRANCISCO — The Republican presidential candidate who won in Iowa but has trailed in more recent contests, Michael Huckabee, says he won’t be driven from the race by supporters of Mitt Romney, who is eager to consolidate the conservative vote to challenge the front-runner, Senator McCain of Arizona.

In recent days, Mr. Romney’s backers have suggested that Mr. Huckabee is acting as a spoiler in the race and taking votes primarily from Mr. Romney.

Mr. Huckabee turned the tables yesterday, arguing that Mr. Romney’s candidacy is the one with no traction.

“Why doesn’t he drop out? Look at how much money he spent to get the same market share that I’ve got,” the former Arkansas governor told a public affairs forum in San Francisco, the Commonwealth Club. “My message is obviously selling a lot better than his because look at how much he’s had to put behind it to market it, and it’s barely sold. I have fewer resources, but I’ve sold as much of the product as he has.”

Mr. Huckabee said Mr. Romney, who founded a business consulting firm, Bain Capital, should be able to recognize the trend lines. “He’s an MBA and a smart business guy. If he were applying the same kind of business standard that he applied at Bain Capital, he’d be saying Huckabee’s got a more efficient operation. They’re getting a better market share than me for less money. Let’s invest in him,” the former Arkansas governor said.

A spokesman for Mr. Romney, Kevin Madden, said the former Massachusetts governor has “growing support” and won in three states. The aide called Mr. Huckabee’s record on taxes and spending “abysmal.”

In the liberal Bay Area, however, it is his stance on many social issues that is sharply at odds with the prevailing views. About 150 people turned out for Mr. Huckabee’s lunchtime presentation at a San Francisco hotel. Many of them were already his supporters.

The Arkansas governor made bold claims about his signature “Fair Tax” proposal, which calls for a national sales tax to replace income, fuel, and inheritance taxes. “It would make a dramatic difference. We wouldn’t be in a recession, and we wouldn’t be worrying about how we are going to bring back the 3 million manufacturing jobs we have lost,” he said.

Mr. Huckabee dismissed the notion that the tax proposal was too radical to be passed by Congress. “Let’s ask the most important question, is this a superior approach to the tax structure in this country than the one we have? If the answer is yes, then please don’t tell me that this country is incapable of doing the best,” he said.

At one point, the program was interrupted by two women who shouted about the deaths of children in Iraq. The women were hustled out, but Mr. Huckabee said the episode should instill confidence in America. “It’s a wonderful affirmation of who we are as a country,” he said. “Try that in Cuba, try that in Iran, and see if you’ll be sleeping in your own bed tonight,” he said.”

At a news conference, Mr. Huckabee asked journalists not to prejudge the outcome of the race, since only 8% of delegates have been picked. He noted that the conventional wisdom about candidates like Mayor Giuliani and Fred Thompson was far from clairvoyant.

“Fred’s gone. Rudy’s gone. McCain’s resurrected. I’m in contention,” Mr. Huckabee said. “Everything people said even four months ago has turned out to be absolutely, 180-degrees wrong. When people are saying Huckabee can’t win, I just want to say, ‘Let’s check on that four months from now.'”