NASHUA, N.H. — As he campaigns here among die-hard Republicans, Mitt Romney is taking aim at the top tier of Democratic presidential candidates — chiefly Senator Clinton, accusing her of advocating an economic policy in line with Karl Marx.

Speaking yesterday to the Nashua Republican City Committee, the former Massachusetts governor criticized the three leading Democratic contenders — Mrs. Clinton, Senator Obama of Illinois, and a former senator of North Carolina, John Edwards — on a number of domestic and international issues. He also contrasted his background as a former governor and businessman with that of his Democratic rivals. The group that Mr. Romney addressed was comprised of local Republicans backing a host of different presidential candidates. He was the only one to speak in person to the group of fiscal and social conservatives. The group displayed a box carrying an audio version of Lou Cannon’s biography of Ronald Reagan in connection with a fund-raiser.

“None of them has ever managed a private enterprise or lead a state, and their solutions would take us in exactly the wrong direction,” Mr. Romney said. “Their solutions are Big Brother, big taxes, and big government, and that is not the right answer for America.” Later, he told The New York Sun that “in the case of the three Democratic front-runners, none of them has managed a corner store, let alone a state or a city or an enterprise of the nature of the United States.”

Mr. Romney referred to recent comments that Mrs. Clinton made about the economy. “She said we have been an ‘on-your-own society.’ She said, ‘It’s time to get rid of that and replace it with shared responsibility,'” Mr. Romney said. “That’s out with Adam Smith and in with Karl Marx.” Mr. Romney advocated lowering corporate and personal income taxes as well as a freeze on taxes on savings accounts.

Talking about the prospects of health-care reform, Mr. Romney said, “The right answer is not a government takeover, is not socialized medicine, is not Hillarycare” and quoted writer P.J. O’Rourke, saying, “You think health care’s expensive here, just wait till it’s free.”

On the national security front, Mr. Romney, citing a long line of countries in which terrorists have struck, targeted John Edwards’s comments on the struggle against terrorism. “There is a war being waged by the terrorists, and if I or any other Republican president is running this country, there will be a war waged on the terrorists,” Mr. Romney said.

The former Massachusetts governor also returned to a rhetorical line that he had been using this week, criticizing Mr. Obama’s sex-education plan. “You heard Barack Obama say we ought to have sex education in kindergarten,” Mr. Romney said. “The amount of sex education in kindergarten we ought to be teaching is absolutely zero.

Mr. Romney’s attack lines received applause and sometimes hoots of agreement from members of the audience. His comments won plaudits from state Rep. Nancy Elliot of nearby Merrimack. “The Democrats have really trashed our country and our state. And of course, spending is out of control,” Ms. Elliot said. “His ideas are pure Republican ideas. I think he went over very well with the crowd.”

Mr. Romney’s comments drew ire from Democrats. Mrs. Clinton’s campaign responded to Mr. Romney’s charges referencing changes in his positions. “Given how often Mr. Romney flip-flops, tomorrow he will be touting his membership in the Communist Party,” Blake Zeff, a campaign spokesman, said in a statement.

Mr. Edward’s New Hampshire spokeswoman, Kate Bedingfield, said, “It seems the only thing that Governor Romney has chosen to stand firm on is the misguided, out-of-touch belief that we should continue with George Bush’s failed foreign policy in Iraq.”

Still, local Republicans warmed to him. “He is not afraid to point out differences between himself and those on the other side of the aisle,” state Rep. Pamela Price, who is backing Mr. Romney, said. Saying that Mr. Romney’s presence at the lunch had helped the Republicans increase attendance at the event, Ms. Price of Nashua, added, “The crowd thinks he’s great. And he is gaining ground.” Gaining the support of grassroots Republicans can help a candidate build a machine of field operatives. The New Hampshire primary still turns, in part, on the strength of field organizations, which can identify voters and earn a candidate votes on election day.

Asked later about his concentration on the Democratic — not Republican — candidates for the presidency, Mr. Romney said, “This is a Republican luncheon, not a Romney rally.” Queried as to the management qualifications of a former governor versus a mayor, such as his opponent, Mayor Giuliani, Mr. Romney said, “I’m not going to make those fine distinctions.”

When Mr. Romney visited Brown’s Lobster Pound in Seabrook, N.H., late yesterday afternoon, there seemed to be an appetite for something other than just fresh seafood. “I’m not voting for Hillary,” said Paul Currier of Derry, wearing a black Harley-Davidson T-shirt. “We don’t need a more sensitive government in Washington.”