CHARLOTTE — Campaigning his way toward the Democratic National Convention, President Barack Obama slapped a “Romney doesn’t care” label on his rival’s health-care views Sunday and said Republicans want to repeal new protections for millions without offering a plan of their own.

Vice President Joe Biden swiftly broadened the attack, accusing Republicans of seeking to undermine the decades-old federal program millions of seniors rely on for health care. “We are for Medicare. They are for voucher care,” he said.

The president and vice president campaigned separately across three battleground states as delegates descended on the Democrats’ convention city for two days of partying before their first official meeting Tuesday in the Time Warner Cable Arena.

An enormous sand sculpture made in Obama’s likeness served as a reminder, as if any were needed, that the Democrats were in town.

Some 800 demonstrators marched through the streets around the convention hall, protesting what they call corporate greed as well as U.S. drone strikes overseas, said to kill children as well as terrorists. Dozens of police officers walked along with the protesters’ parade, carrying gas masks, wooden batons and plastic hand ties. One arrest was reported, for public intoxication.

The economy is the dominant issue of the campaign, and Biden’s itinerary, in particular, underscored the threat that a sluggish recovery and high, 8.3 percent unemployment pose to Democrats seeking another term in power. He was in Pennsylvania and Wisconsin, states that have received little attention previously as the candidates, their parties and outside allies concentrate on the areas of the country deemed most competitive. His presence suggested the race in both states was tightening.

Romney spent Sunday at his Wolfeboro, N.H., vacation home, leaving only to attend church services with his wife, Ann.

Aides said he would spend much of the Democrats’ convention week preparing for three fall debates with Obama, beginning on Oct. 3.

Running mate Paul Ryan was booked into North Carolina, counterprogramming the Democratic convention rhetoric.

Biden’s appearance in Green Bay, Wis., was mostly devoted to domestic issues.

Earlier, campaigning in York, Pa., he took a swipe at Romney on foreign policy.

“He said it was a mistake to end the war in Iraq and bring all of our warriors home,” the vice president said. “He said it was a mistake to set an end date for our warriors in Afghanistan and bring them home. He implies by the speech that he’s ready to go to war in Syria and Iran. “

Obama and Biden will be nominated for second terms on Wednesday night, when former President Bill Clinton has the role of star speaker.