To prepare for his biggest test yet on the national stage, untested debater Paul Ryan has been hauling two thick briefing books around the country and intently studying up on Vice President Joe Biden, who has been sparring over public policy since the Wisconsin congressman was learning how to talk.

Ryan, the 42-year-old Republican vice presidential nominee, has suggested his youth will be an asset in connecting with voters at the sole vice presidential debate Thursday in Kentucky against the 69-year-old former senator. But risks abound for the GOP rising star, who hasn’t participated in a campaign debate since his first run for office 14 years ago.

The main goal for Ryan’s inner-circle: get him comfortable answering questions in broad terms that connect with voters and avoid the wonky, in-the-weeds answers more appropriate for a budget hearing than a living room.

Ryan’s team wants to keep him talking about positive changes a Romney-Ryan administration would mean for the country, not a full-throated defense of the campaign’s sometimes nebulous math.

As the House Republicans’ top budget writer, aides say Ryan is confident he can handle questions about federal spending and taxes. He is a bit more nervous on international affairs – and for good reason. Ryan was thrust into the national spotlight a few months ago when he joined the Republican ticket but has limited exposure in that arena.