WASHINGTON -- Mitt Romney's selection of Paul Ryan as his running mate brought Medicare to the forefront of the presidential campaign, as Democrats tried to tie Romney to Ryan's proposal to redesign the health insurance program. Since the Ryan pick, the two campaigns have traded barbs and attack ads attempting to portray the other as undermining Medicare. Surveys released this week in several swing states suggest that President Barack Obama has strengthened his lead on the issue, which could be a problem for Romney in key states like Florida and Ohio.

According to Washington Post/Kaiser Family Foundation polls conducted in Florida, Ohio and Virginia and released Thursday, registered voters trust Obama over Romney to handle Medicare by wide margins. Respondents preferred Obama on the issue by 53 percent to 38 percent in Florida, 56 percent to 37 percent in Ohio and 52 percent to 39 percent in Virginia. More than 70 percent of voters in each state said they consider Medicare either "very" or "extremely" important to their vote.

Similarly, CBS/New York Times/Quinnipiac surveys in Florida, Ohio and Pennsylvania found that likely voters think Obama would do a better job than Romney on handling Medicare: 55 percent to 40 percent in Florida, 55 percent to 39 percent in Ohio and 55 percent to 39 percent in Pennsylvania.

A USA Today/Gallup poll in 12 swing states found a smaller advantage for Obama: 50 percent to 44 percent. The Gallup poll pooled registered voters in the 12 states and did not break results out for individual states.

Although most voters surveyed in the Washington Post/Kaiser polls said they thought Medicare needed changes to sustain it for the future, Florida and Ohio voters who thought Medicare needed changes were almost evenly split on whether those ought to be major or minor reforms. Their Virginia counterparts were more likely to say that Medicare needed major reform.

More specifically, when asked to choose between a future in which Medicare would "continue as it is today, with the government guaranteeing all seniors the same set of health insurance benefits," or one in which Medicare would "be changed to a system in which the government guarantees each senior a fixed amount of money to help them purchase coverage either from traditional Medicare or from a list of private health plans," most Washington Post/Kaiser respondents said they preferred the traditional model. This was especially true in Florida, where voters prefer keeping Medicare as it is by a margin of 65 percent to 29 percent.

National surveys suggest that the preference for Obama on Medicare crystallized over the summer. A national CBS/New York Times poll, conducted Sept. 8-12, found that registered voters favored Obama over Romney on Medicare 52 percent to 40 percent. Their previous poll, conducted Aug. 22-26, had found a more even split: 45 percent to 44 percent. Similarly, ABC News/Washington Post polls conducted Aug. 22-25 and Sept. 7-9 saw registered voters switch from favoring Romney on the issue in August (45 percent to 42 percent) to favoring Obama in September (48 percent to 43 percent). A Kaiser Family Foundation survey conducted Sept. 13-19 found that adults nationwide trust Obama over Romney on Medicare by 20 percentage points (52 percent to 32 percent), up from 10 points (44 percent to 34 percent) in July.

The ABC News/Washington Post polls also found increases in preference for Obama over Romney on a number of other issues, such as the economy, budget deficit, taxes and international affairs, but the rise in Obama support on Medicare was among the bigger changes. Notably, Obama's advantage on health care as a whole did not increase between the August and September surveys.

It's unclear whether those responding negatively to Romney on Medicare know much about the specifics of the GOP nominee's position. One possibility is that Democrats have been successful in tying Romney to Ryan's budget plans, which he proposed as chairman of the House Budget Committee. On Wednesday, Priorities USA Action, a pro-Obama super PAC, released polls conducted earlier this month that found more voters in five states -- Florida, Ohio, Colorado, Wisconsin and Iowa -- oppose than support Ryan's budget proposal. The survey questions did not specifically inform respondents that the Ryan budget might affect the future of Medicare.

Separating voter support on a particular issue from overall preference for a candidate can be difficult, since voters who support a candidate are likely to also say they prefer that candidate on specific issues. But in each of the states surveyed by the Washington Post/Kaiser and CBS/New York Times/Quinnipiac pollsters, voter preference for Obama on Medicare outstripped Obama's lead in the presidential race.

The president's Medicare advantage could make things especially difficult for Romney in a state like Florida, where seniors are a key voting bloc and Romney is running behind in recent polls. If current surveys are any indication, Romney's attempts to portray Obama as bad for Medicare have fallen on deaf ears.

The new Washington Post/Kaiser polls were conducted Sept. 19-23 among 925 registered voters in Florida and 934 registered voters in Ohio. The Virginia poll was conducted Sept. 12-16 among 934 registered voters. All three surveys have a margin of error of four percentage points. The national Kaiser Family Foundation poll was conducted Sept. 13-19 among 1,534 adults and has a three-point margin of error.

The CBS/New York Times/Quinnipiac polls were conducted Sept. 18-24 among 1,196 likely voters in Florida, 1,162 likely voters in Ohio and 1,280 likely voters in Pennsylvania. The Florida survey has a 2.8-point margin of error, while the Ohio and Pennsylvania surveys have a 2.9-point margin of error.

Also on HuffPost:

Loading Slideshow...
  • Colorado

    <strong>For more presidential and congressional polls, maps and forecasts, <a href="http://elections.huffingtonpost.com/2012/romney-vs-obama-electoral-map?hw" target="_hplink">visit HuffPost Pollster</a>.</strong>

  • Iowa

    <strong>For more presidential and congressional polls, maps and forecasts, <a href="http://elections.huffingtonpost.com/2012/romney-vs-obama-electoral-map?hw" target="_hplink">visit HuffPost Pollster</a>.</strong>

  • Wisconsin

    <strong>For more presidential and congressional polls, maps and forecasts, <a href="http://elections.huffingtonpost.com/2012/romney-vs-obama-electoral-map?hw" target="_hplink">visit HuffPost Pollster</a>.</strong>

  • Ohio

    <strong>For more presidential and congressional polls, maps and forecasts, <a href="http://elections.huffingtonpost.com/2012/romney-vs-obama-electoral-map?hw" target="_hplink">visit HuffPost Pollster</a>.</strong>

  • Virginia

    <strong>For more presidential and congressional polls, maps and forecasts, <a href="http://elections.huffingtonpost.com/2012/romney-vs-obama-electoral-map?hw" target="_hplink">visit HuffPost Pollster</a>.</strong>

  • North Carolina

    <strong>For more presidential and congressional polls, maps and forecasts, <a href="http://elections.huffingtonpost.com/2012/romney-vs-obama-electoral-map?hw" target="_hplink">visit HuffPost Pollster</a>.</strong>

  • Florida

    <strong>For more presidential and congressional polls, maps and forecasts, <a href="http://elections.huffingtonpost.com/2012/romney-vs-obama-electoral-map?hw" target="_hplink">visit HuffPost Pollster</a>.</strong>