TAMPA -- He’s just the running mate. But Americans could be more eager to see Paul Ryan when he takes the stage Wednesday at the Republican National Convention than the man at the top of the ticket, Republican presidential nominee Mitt Romney.

Ryan is the newest thing in politics right now, the still largely unknown subject of wild enthusiasm among conservatives, the target of unrelenting scorn from Democrats. In a prime-time speech Wednesday, he gets to tell his own story unfiltered by the news media. It will be a critical test, as he works to drive his party to a march-to-the-polls frenzy while not doing anything that could turn off independents and suburban moderates who could decide a close election.

Young, attractive and upbeat, the Republican vice presidential nominee easily energizes Republican activists — some of whom question Romney’s conservative credentials —largely for his blueprint to slash the federal government.

“I adore him,” gushed Kathy Hildebrand, a former math teacher and a convention delegate from Georgia. “He offers real solutions.”

But it’s precisely those solutions —policy proposals that include overhauling Medicare — that make him less popular with Democrats and moderates needed to win in November.

“His back is to the wall, frankly,” said John Zogby, an independent pollster. “He’s going to have a rough time going to the middle.”

The middle — and maybe more — will be watching. Slightly more Americans are interested in hearing from Ryan that Romney, according to a poll Tuesday from the nonpartisan Pew Research Center. Pew found that 46 percent were very or somewhat interested in hearing Ryan’s speech, while 44 percent felt the same about Romney’s speech.

Romney’s pick of Ryan as his running mate elated conservatives skeptical about Romney’s bona fides and surprised analysts who predicted that the cautious Romney would opt for a safer pick, without the track record of proposals to overhaul popular entitlements such as Medicare, the popular health insurance program for the elderly. The program faces insolvency without changes, but Democrats hammer most Republican proposals and Ryan’s in particular as a threat to the program rather than a help.

Initial polls showed Romney may have gained a point or two with Ryan — in line with recent vice presidential choices. Zogby said Ryan has helped Romney improve slightly in the polls to catch up with President Barack Obama. But, he said, while polls shows he appeals more to younger voters, he appeals less to older voters, possibly because of concerns about changes to Medicare.

As chairman of the House Budget Committee, Ryan has quickly emerged as one of the party’s top policy thinkers and leaders, touting spending cuts, tax cuts to spur growth and changes in entitlements.

His budget plan is regarded as a blueprint for conservatives. It would repeal the 2010 federal health care law, give workers younger than 55 the option of taking a government voucher to buy private insurance rather than Medicare, give states more say over Medicaid, the program for the poor, and limit government spending to 20 percent of the economy by 2015. With the recession inflating demand for government services, federal spending has reached as much as 24 percent of the total economy.