MILWAUKEE — President Obama traveled to the home turf of his opponent’s running mate, Representative Paul D. Ryan, on Saturday, reprising his attack on Mitt Romney for remarks he made behind closed doors characterizing Obama voters as the 47 percent of the population who depend on government handouts and do not pay federal income taxes.

“We can’t get very far if we’re just writing off half the country as a bunch of victims, or presume that somehow they want to be dependent on government or don’t want to take responsibility for their own lives,” Mr. Obama said to donors at a fund-raiser in a historic theater in Milwaukee. “Wherever I travel, folks are working hard.”

Speaking later at a boisterous rally, Mr. Obama said Mr. Romney’s vision had no room for struggling middle-class families, the elderly, students burdened by college loans or veterans returning from wars in Iraq and Afghanistan.

“Their basic philosophy is ‘you’re on your own,’ ” Mr. Obama said, standing under a packed lakeside pavilion, where a rainbow briefly colored the sky before a rainstorm. He rejected a philosophy that he said pinned the blame for the country’s problems on gay people, immigrants, unions and other groups.