Updated

Presidential hopeful Mitt Romney took aim at Democratic rivals on Sunday, calling them all unprepared to lead the country and comparing Sen. Hillary Rodham Clinton's economic plan to that of Socialist Karl Marx.

"It would be helpful to have a person leading the country who understands how the economy works and has actually managed something," the former Massachusetts governor told reporters after a GOP fundraiser. "In the case of the three Democratic frontrunners, not one of them has managed even a corner store, let alone a state or a city."

It was a central theme of Romney's day while campaigning in the early voting state and blasting Clinton, Sen. Barack Obama and former Sen. John Edwards.

Romney, who has gained in early state polling and leads in New Hampshire, in recent weeks has focused his criticism on Democrats, particularly Clinton, rather than rival Republicans. It's a strategy he hopes will help him maintain leads over Sen. John McCain and former New York Mayor Rudy Giuliani.

"I wanted to focus on the Democrats," he said. "By and large, the best way to further my interest is to let people know what I would do and to distinguish that from what the Democrats would do."

Earlier Sunday, Romney was in Washington courting Hispanic voters by extolling the virtues of faith, family values and immigration. Candidates in both major parties are reaching out to Hispanic voters, underscoring their status as the largest and fastest-growing minority group in the 2008 campaign.

"If you say, name people who are hardworking, seek education, love God, love their families and value freedom, — it's Hispanic-Americans, just like other Americans," Romney told a crowd at the Republican National Hispanic Assembly's annual convention.

Praising Hispanics as "quintessentially American," Romney said the nation's immigration policy should open doors for people with such strong beliefs. "I want to make sure we continue an open door in immigration that welcomes people who come here with those kinds of values," he said.

During an Iowa visit last week, Romney struck a hard line on illegal immigration. He criticized Giuliani for making the city "a sanctuary city for illegal aliens" by failing to enforce the immigration laws on the books. Romney also noted that as governor, he had deputized state police to enforce immigration laws and denied driver's licenses to illegal immigrants.