President Barack Obama launched an attack Wednesday on congressman Paul Ryan's plan to reform Medicare, a divisive issue that has obscured Republican attempts to make the White House election campaign all about jobs.

Mitt Romney's announcement of Ryan as his vice presidential running mate on Saturday energized the Republican campaign but brought the health insurance program into focus due to the Wisconsin congressman's controversial budget plan that includes reform of Medicare.

"They want to turn Medicare into a voucher program," Obama told a crowd in Dubuque, Iowa. "And because the voucher wouldn't keep up with costs, the plan ... would force seniors to pay an extra $6,400 a year, and I assume they don't have it."

Ryan proposes giving retirees an allowance to buy their own coverage. Democrats say that would raise costs for seniors and reduce the quality of their care.

The United States traditionally has low voter turnout on election day in November, but senior citizens go to the polls in droves, making them a highly sought-after constituency.

Winning Florida, another battleground state with a high population of elderly Americans who rely on Medicare, may be easier for the Obama team on November 6 because of Ryan's addition to the ticket.

"I have strengthened Medicare," Obama said. "I've proposed reforms that will save Medicare money by getting rid of wasteful spending in the health care system. Reforms that will not touch your Medicare benefits, not by a dime."

OBAMACARE AND MEDICARE

Romney, however, is fighting back with criticism that Obama cut $716 billion from Medicare to help fund his 2010 healthcare reform legislation, known as Obamacare.

"If I become president, I'm going to restore that $716 billion to the Medicare trust fund so that current seniors can know that the trust fund is not being raided and get Medicare on track to be solvent long-term on a permanent basis," Romney said on "CBS This Morning" on Wednesday.

Government funds set aside for Medicare are expected to be exhausted in 2024.

Romney tried to distance himself from Ryan's budget plan, criticized by Democrats as relying on harsh spending cuts that would ruin the safety net for the poor and elderly.

The former governor of Massachusetts said he, not Ryan, would direct economic policy.

"First of all, Congressman Ryan has joined my campaign, and his campaign is my campaign now, and we're on exactly the same page," he said.

A Gallup survey on Wednesday showed Romney received no immediate poll boost from taking Ryan onto his team, although he leads Obama by 47-45 percent among registered voters.

The fight over Medicare and other fiscal issues overshadows Romney's message that Obama is failing to tame unemployment, running at 8.3 percent, and does not understand business.

Back-and-forth accusations over dishonest ads and rhetorical low blows also kept the jobs issue on the margins of the campaign.

"We're now in attack and blame, smear and fear. The president doesn't have a record to run on...People are going to see through this, I just don't think people are going to fall for this time around," Ryan told the Sean Hannity radio show.

Vice President Joe Biden triggered outrage from Romney on Tuesday by saying the Republican would put people "in chains" if elected president.