Democratic presidential candidates courted the fast-growing Hispanic electorate on Sunday night by debating on a Spanish-language television network, where they promised to swiftly overhaul the immigration system and accused Republicans and President Bush of stoking anti-Hispanic sentiment.

The three leading candidates, Senators Hillary Rodham Clinton of New York and Barack Obama of Illinois and former Senator John Edwards of North Carolina, had especially sharp criticism for leaders of the Republican Party. They expressed concerns that Republicans were enabling anti-immigrant feelings and even racist attitudes, or at least not taking a tougher stand against them.

Mrs. Clinton said legislative proposals to overhaul the immigration system, which all the Democrats at the debate endorsed, had been used by Republicans and some in the news media to ''bash immigrants'' and engage in demagoguery.

''The Republican candidates need to understand that they are doing a great disservice to our country,'' she said.

Later, Mrs. Clinton added: ''There are many in the political and frankly in the broadcast world today who take a particular aim at our Latino population. I think it's very destructive.'' A spokesman for Mrs. Clinton said after the debate that she was referring to the CNN anchor Lou Dobbs and the radio host Rush Limbaugh, among others.

Mr. Obama, who is seeking strong support from both black and Hispanic voters, recalled a telegram the Rev. Dr. Martin Luther King Jr. sent to Cesar Chavez when the two men were each involved in protest strikes. The telegram read, ''Our separate struggles are one.''

''That's what's been missing from presidential leadership -- explaining to the American people from all walks of life that our separate struggles are one,'' Mr. Obama said. ''A president has to not only speak up forcefully against anti-immigrant sentiment and racist sentiment, but also make sure that all workers are being tended to.''

Mr. Edwards put the blame on President Bush for divisive attitudes that can lead to anti-Hispanic sentiment, saying he ''uses absolutely every tool available to him politically to divide the country.'' Mr. Edwards added, ''This needs to be brought to an end.''

The debate was an opportunity for the candidates to reach some of the 17 million eligible Hispanic voters in the United States in a primary season when they are expected to have a greater voice because of early contests in California and New York. It also allowed some of the candidates to highlight their ties to Hispanics. Gov. Bill Richardson, the only Hispanic running for the party's nomination, spoke a few lines of Spanish during the debate; Senator Christopher J. Dodd, the only other Democratic contender fluent in Spanish, used a bit as well.

''I am very proud of being a Latino,'' Mr. Richardson said in Spanish at the start before a moderator reminded him to speak English.

''I'm disappointed today that 43 million Latinos in this country, for them not to hear one of their own speak Spanish is unfortunate,'' Mr. Richardson said to applause in the debate hall at the University of Miami.

Yet neither Mr. Richardson nor Mr. Dodd, when asked, said they would support promoting Spanish as the second official language of the United States. Representative Dennis J. Kucinich of Ohio, who was also asked, did embrace the idea.

The candidates generally focused on policies to support legal immigration and immigrants, and to a lesser extent on border security, unlike the Republican candidates, who tend to stress enforcement. (One of the eight Democratic candidates, Senator Joseph R. Biden Jr. of Delaware, did not attend the debate to prepare for Senate headings this week, a spokeswoman said.)

None of the Democrats made any especially bold moves, although Mr. Dodd and former Senator Mike Gravel of Alaska said they would take steps to end the trade embargo with Cuba, and Mr. Richardson said he would consider it if President Fidel Castro released political prisoners.

Mr. Dodd said that he would have a robust foreign policy in Central and South America and that the Bush administration had faltered in building relations and projecting a positive image of America to nations there.

''We shouldn't be losing a public relations battle to Hugo Chávez,'' Mr. Dodd said, referring to the leader of Venezuela.

Mr. Obama, Mrs. Clinton and Mr. Dodd were pressed about their support for a barrier along the Mexican border and asked why they would not support a similar wall along Canada.

Mr. Obama did not address the distinction between Mexico and Canada, talking instead about his support for an immigration overhaul and border security. Mrs. Clinton said she supported ''much more border patrolling and much more technology'' on both borders, and a barrier ''in certain areas.'' Mr. Dodd echoed Mrs. Clinton, then focused on making trade and economic agreements that benefited Central American countries.

Mr. Richardson, meanwhile, criticized the notion of a barrier on the Mexican border as ''a horrendous example of Washington misguided policy.''

''If you're going to build a 12-foot wall,'' Mr. Richardson said, ''you know what's going to happen? A lot of 13-foot ladders.''

The candidates did not offer major new ideas about fixing immigration, but sought instead to emphasize the intensity they would bring to the issue. Most of them said they would try to overhaul immigration in their first year in office and would include a path to citizenship for illegal immigrants, penalties for employers who hire illegal immigrants and tougher border security.

Mr. Kucinich said the problem of illegal immigration stemmed partly from trade agreements like Nafta, which he said he would cancel as president. He said wrongheaded policies were to blame for illegal immigration, not the people themselves.

''There are no illegal human beings,'' he said to applause.

Several of the Democratic candidates, who as a field generally support withdrawing American troops from Iraq, said they did not expect a coming military report on conditions in Iraq to persuade them to change their views on ending the war.

America's top commander in Iraq, Gen. David H. Petraeus, is scheduled to speak to Congress on Monday, and some of the Democrats suggested that his testimony would be skewed rather than objective.

''What I'm concerned about, about the Petraeus report,'' Mr. Edwards said, ''is that it will basically be a sales job by the White House, that it'll be a P.R. document.''

Mrs. Clinton said that nothing General Petraeus told Congress would persuade her to endorse the Bush administration's current strategy in Iraq.

''There is no military solution; that has been said for years now,'' Mrs. Clinton said. ''That is why I believe we should start bringing out troops home.''

Mr. Obama agreed that the current course in Iraq would only lead to ''the same problems that we've had,'' and called explicitly on Republican members of Congress to turn on Mr. Bush and support a timetable for withdrawal.