At a forum for Latino voters Thursday in Florida, President Obama accused Republicans of thwarting his immigration efforts and mocked GOP rival Mitt Romney for suggesting that nearly half the country was overly dependent on government help.

“When you express the attitude that half the country considers themselves victims and wants to be dependent on government, my thinking is that you haven’t gotten around a lot,” Obama said of Romney.

Even as he criticized the GOP for failing to work with him, Obama said one of his biggest failures in office was his inability “to change the tone in Washington.”

“I’ve learned some lessons,” he said. “Most important is, you can’t change Washington from inside, only from the outside. That’s how some of our biggest accomplishments like health care got done — mobilizing the American people.”

Romney seized on Obama’s comment, saying that the president was conceding failure: “The president today threw in the white flag of surrender again. He said he can’t change Washington from the inside. He can only change it from outside. Well, we’re going to give him that chance in November. He is going outside,” Romney said to a crowd of about 4,500 people. “I can change Washington, and I will change Washington. We’ll get the job done from the inside. Republicans and Democrats will come together. He can’t do it. His slogan was ‘Yes, we can’; his slogan now is ‘No, I can’t.’ This is time for a new president.”

Obama’s comments gave Romney a fresh talking point as his campaign seeks a course change by offering more details, beefing up public appearances and running more ads. Romney has also highlighted a comment by Obama in 1998 in favor of “redistribution.”

The Obama campaign said that Romney was misquoting the president.

“Once again, Mitt Romney is trying to take the heat off himself by taking the president’s words wildly out of context. That’s twice in just 48 hours, which sets a new record in desperation,” Obama campaign spokeswoman Lis Smith said in a statement. “What the president said today is no different than what he has been saying for many years — that change comes from outside Washington, not inside.”

Romney’s “47 percent” remarks, made at a private fundraiser in May, have dogged the candidate in recent days, after a video recording released this week showed him writing off Americans who did not pay income taxes as Obama supporters who would never vote for him. He put that number at 47 percent.

Romney used his own appearance at the same forum hosted by Univision at the University of Miami a day earlier to try to repair some of the fallout from the videotaped comments, declaring that his campaign represented “100 percent” of Americans.

Obama poked Romney for the remarks, telling Univision host Jorge Ramos that “people want a hand up, not a handout” after the recent economic recession.

“Are there people who abuse the system? Yes,” he said. “Both at the bottom and the top, because there are a whole bunch of millionaires not paying taxes either.”

Obama has heavily courted the Latino vote, touting a recent immigration directive to stop deporting some illegal immigrants who were brought to the country as children and have gone on to be productive and law-abiding residents. The president won 67 percent of the Latino vote in 2008, compared with John McCain’s 31 percent, and polls show him leading Romney by a large margin with that group.

During an hour-long question-and-answer session before an audience of students and Democratic supporters, Obama blasted Republicans for standing in the way of his efforts to reform immigration laws, a major area of concern for many Latino voters.

More than once, Ramos pressed Obama for failing to keep his promise, made in 2008, to champion a comprehensive immigration ­reform bill during his first year in office.

“A promise is a promise,” Ramos said.

Obama bristled at the suggestion that he was to blame, saying that congressional Republicans, even some who had supported reform efforts under previous administrations, blocked his administration’s efforts at developing a bipartisan proposal.

“I’m happy to take responsibility for being naive,” Obama said, “that Republicans who previously supported immigration reform . . . would suddenly walk away.”

The president added that: “We have to have cooperation from all sources in order to get something done. . . . I did not promise I would get everything done 100 percent when I was elected. I did promise I would work hard every day to be sure everyone, no matter who you are or where you come from . . . gets a fair shot at the American Dream. That’s a promise I’ve kept.”