TAMPA, Fla. - Voters believe Mitt Romney and other Republicans are more likely to cut Medicare than President Obama and congressional Democrats, according to the latest The Washington Times/JZ Analytics survey, released Sunday.

Ever since Mr. Romney tapped Rep. Paul Ryan, chairman of the House Budget Committee and architect of an overhaul that would change Medicare, the federal health care program for the nation's seniors has been a chief topic of the campaign.

Mr. Obama has accused Mr. Romney and Mr. Ryan of embracing a plan that would end Medicare as it's now constructed, while the GOP says the president's health care law cut more than $700 billion out of Medicare.

By a 46 percent to 27 percent margin, voters said they thought Republicans were the more likely cutters.

The conversation apparently has taken a toll on Mr. Romney among older voters. In July's The Times/JZ Analytics survey, Mr. Romney held a 5-percentage-point lead among voters 65 and older. But that has evaporated and Mr. Obama leads in the new survey, 50 percent to 45 percent, among those voters.

Mr. Obama has pushed that advantage, using his weekly radio address this weekend to say there has been "a lot of accusations and misinformation flying around" about Medicare.

He also said it's Republicans, not he, who want to see cuts.

"They want to turn Medicare into a voucher program. That means that instead of being guaranteed Medicare, seniors would get a voucher to buy insurance, but it wouldn't keep up with costs," he said. "It would effectively end Medicare as we know it."

Mr. Romney, though, argued that it's Mr. Obama's health care law that has taken money out of the Medicare system.

"The way the president cut Medicare, $716 billion for current retirees, that's a real problem," he said on "Fox News Sunday."

Mr. Ryan's budget proposed major changes to Medicaid, the federal-state health care program for the poor, and called for a voucherlike program for Medicare for those 55 and younger.

Voters were evenly split on Mr. Ryan's budget, 42 percent to 42 percent - though among independents it was a little more favorable, at 43 percent to 36 percent.

Two weeks after Mr. Romney selected Mr. Paul as his running mate, the congressman from Wisconsin has excited many conservative Republicans and appeared to put his home state of Wisconsin in play in November, but failed to win over a broader audience.

The Times/JZ Analytics Survey of 800 likely voters, taken Thursday through Saturday, found Mr. Ryan hasn't upstaged Mr. Romney - a fear some Republicans had about other potential running-mate choices such as New Jersey Gov. Chris Christie or Sen. Marco Rubio of Florida.

Indeed, asked whom they would rather see at the top of the Republican ticket, voters overwhelmingly gave Mr. Romney the nod over Mr. Ryan, 51 percent to 22 percent. Among Republicans, it was an even stronger 69 percent to 22 percent margin, or 3-to-1.

The survey then asked whether voters would rather see Mr. Obama or Hillary Rodham Clinton, his 2008 opponent and his secretary of state, and the results were much closer, with Mr. Obama topping Mrs. Clinton by 44 percent to 40 percent. Among Democrats, though, Mr. Obama held a comfortable 70 percent to 26 percent lead.

John Zogby, the pollster who conducted the survey, said at the beginning of the year that many Democrats were disappointed in the president, but he has overcome that.

"Obama's clearly consolidated his base, that's what all the numbers show, and we always kind of figured he's going to use the opening salvo at his convention next week to try to appeal to swing voters," Mr. Zogby said.

The poll had a margin of error of 3.5 percentage points.

Data, Xtabs and Methodology for the Nationwide Poll