Which side is winning the battle to define Paul Ryan?

So far, polls show little to no bounce for Mitt Romney since he named Rep. Paul Ryan as his running mate. The wisdom of adding Ryan to the ticket could be decided by how well he and Romney resolve their unsettled message on Medicare.

The moment Mitt Romney announced that Rep. Paul Ryan was his running mate, the race to define the youthful budget wonk from Wisconsin was on.

Would the public see him as a dynamic reformer, ready to help Mr. Romney steer the nation away from insolvency and onto a robust fiscal and economic path? Or would voters see him as a conservative ideologue, ready to undo the social safety net and hand tax cuts to the rich?

Chances are, it depends on where one already stands. Most likely, voters already know which team they’ll support in November, and judging by the polls, the selection of Mr. Ryan has barely made a dent in what is shaping up to be a close race. Gallup Daily tracking shows Romney at 47 percent, compared with 46 percent for the four days before he named Ryan. President Obama has held steady at 45 percent. Gallup’s 1-point bump is in line with the average of polls taken since Saturday.

“This is a below-average ‘bounce’ for the selection of a vice presidential candidate,” writes Nate Silver, the numbers-crunching blogger at The New York Times. ”In past elections, the bounce has averaged in the neighborhood of 4 percentage points instead.”

The Obama campaign is predictably gleeful, and held a conference call Thursday to highlight the polls – including a YouGov poll that showed Mr. Obama picking up a percentage point since the Ryan news. But it’s early in the season, and many voters are still tuning in to this new figure on the national stage.

In fact, some analysts suggest that Romney was not even aiming for a splashy debut of his running mate. Making the announcement on a Saturday morning on the final weekend of the Summer Olympics more than two weeks before the start of the Republican convention was not a typical rollout. Perhaps the goal was to wow activists, who already know about Ryan and his bold conservative vision, and let the rest of the electorate get to know Ryan over time.

At the introductory event in Norfolk, Va., last Saturday, Romney emphasized character and leadership in describing Ryan. He also invoked key touchstones: Ryan's Catholicism, his father’s early death, his wife and children, his Janesville, Wis., roots.

“In a city that is far too often characterized by pettiness and personal attacks, Paul Ryan is a shining exception,” Romney said. “He does not demonize his opponents. He understands that honorable people can have honest differences.”

Likewise, Democrats are not trying to demonize Ryan personally. They are granting that he is personally likable – a quality that Romney has struggled to project – and instead are zeroing in on his budget plan.

“Mitt Romney and Paul Ryan plan to end Medicare as we know it,” screams the headline on a Youtube video posted by the Obama campaign on Aug. 15. That just about sums up the critique of Ryan so far: nice guy, but watch your pocketbook.

Add to the conversation a discussion of the Ayn Rand-ian philosophy that Ryan explored while in high school as he coped with the death of his father. Some of the Russian emigré novelist’s “objectivist” views – particularly the emphasis on self-reliance – influenced Ryan’s outlook, though he rejected her atheism.

But it’s the future of Medicare – the federal government’s health insurance program for seniors that is heading toward insolvency – that dominates the conversation about Ryan, for now. For Americans currently under age 55, he proposes to remake the program into a voucher-like system, while also offering traditional fee-for-service Medicare as an option.

Ryan says his approach encourages more competition among insurers and makes the system more efficient. Democrats say the reform would underfund health care for seniors.

Proponents of Ryan’s selection as running mate argued that because the campaign was going to be about entitlement programs anyway, Romney should put the author of the Republican plan out there to explain it. For now, the choice has created some awkward moments, as Romney has said his plan differs from Ryan but has yet to release the details.

Ryan's selection has also produced some internal fireworks among Republican leaders. Blind quotes in the media raising concerns that the Ryan pick could bomb have been met with derision from Ryan’s champions, including The Wall Street Journal editorial page, which called the worriers “bed-wetters.”

It’s not clear how much rank-and-file voters pay attention to inside-the-Beltway chatter. But for now, the jury is out as to which way the Ryan selection will go.

“We’ll know whether it was the right decision at the end of the vice presidential debate” in October, says Dan Schnur, a former Republican strategist. “If Ryan spends more time talking about Medicare than [Vice President] Joe Biden does, then it was worth the risk. If Biden talks more about Medicare than Ryan does, then it probably didn’t pay off.”

Mr. Schnur and other Republicans say there’s still time for Ryan and Romney to get their talking points straight on Medicare. But the GOP ticket can’t spend the whole campaign talking about it. The larger point about Medicare and the other big entitlements – Social Security and Medicaid – is that they need to be put on a path to sustainability. Continued large federal deficits, which add to the already crushing national debt, are increasingly harmful to economic growth, Republicans say.

But starting the campaign with a discussion of entitlement reform instead of the current economy and job creation contains political risk.

“It’s a risk based on the assumption that you can make voters think about economic growth,” Schnur says. “You have to think about deficit reduction as an essential part of economic growth. ... Every 10 years or so, Republicans decide the American people are ready for a difficult conversation about entitlements. And every 10 years, the American people demonstrate that they’re not.”